True Strike, Innate Sorcery, and magic items.

The distinction between keywords and plain text is a fairly important part of 2024 5E, not "hair splitting".

There are no examples of a spellcasting stat in 2024 5E that is not Int, Wis, or Cha. More importantly, there is a distinction between the stat you use for spells - your spellcasting stat - and the stat you use for weapons - Strength or Dexterity. If an effect is using the stat used for weapons, it is a weapon attack rather than a spell attack. This distinction is why True Strike does not have any spell attack roll associated with it (and thus cannot be affected by purely spell-based abilities like Innate Sorcery).

True Strike does not require you make an attack roll as part of its casting. It requires you make an attack roll as part of its resolution. There is no attack roll made during the casting of weapon cantrips like Booming/Green Flame Blade or True Strike. Only once they resolve are you granted a weapon attack which requires a weapon attack roll.

Quote from VerilyRaze >>

 

True Strike does not require you make an attack roll as part of its casting. It requires you make an attack roll as part of its resolution. There is no attack roll made during the casting of weapon cantrips like Booming/Green Flame Blade or True Strike. Only once they resolve are you granted a weapon attack which requires a weapon attack roll.

So, if I understand you correctly, you're saying that you believe a spell like Fire Bolt — which says "Make a ranged spell attack against the target" — is making an attack as part of the spell's "casting", but a spell like True Strike — which says "you make one weapon attack with the weapon used in the spell's casting" — is making an attack as part of the spell's "resolution"?

Setting aside the fact that this distinction between a spell's "casting" and its "resolution" is not really a thing in the rules, I have two questions then:

1. How are we meant to know whether a spell that tells us to make an attack (as both of these spells do) is telling us to make that attack as part of its "casting" or part of its "resolution"?
2. Since Innate Sorcery does not say that it's limited to attacks made as part of a spell's "casting", nor does it say it doesn't apply to attacks made as part of a spell's "resolution", why should it only apply to one and not the other?

The distinction between the spell's casting and resolution is absolutely a thing in the rules. It's why you have to custom edit your D&D Beyond character sheet to accommodate the weapon cantrips but you don't for spells like Firebolt.

In terms of your questions:

1. You know because it explicitly tells you, as I've outlined.
2. Innate Sorcery is limited to attack rolls with spells. True Strike merely gives you a weapon attack. It's no different from the fact that you don't use Innate Sorcery with Haste or Shillelagh.

Quote from VerilyRaze >>

The distinction between the spell's casting and resolution is absolutely a thing in the rules. It's why you have to custom edit your D&D Beyond character sheet to accommodate the weapon cantrips but you don't for spells like Firebolt.

In terms of your questions:

1. You know because it explicitly tells you, as I've outlined.
2. Innate Sorcery is limited to attack rolls with spells. True Strike merely gives you a weapon attack. It's no different from the fact that you don't use Innate Sorcery with Haste or Shillelagh.

Can you please point out exactly where in the rules the "casting" and "resolution" of a spell are defined as two separate things, and where exactly in the description of the spells True Strike and Booming Blade the boundary between these two things is defined? You say it "explicitly tells you", so where exactly is that? It seems like you're reading words that I'm not seeing. Are we looking at two different things?

Here's the text of True Strike, which explicitly tells you to make an attack as part of casting the spell:

Guided by a flash of magical insight, you make one attack with the weapon used in the spell’s casting. The attack uses your spellcasting ability for the attack and damage rolls instead of using Strength or Dexterity. If the attack deals damage, it can be Radiant damage or the weapon’s normal damage type (your choice).

Here's the text of Shillelagh, which does not:

A Club or Quarterstaff you are holding is imbued with nature’s power. For the duration, you can use your spellcasting ability instead of Strength for the attack and damage rolls of melee attacks using that weapon, and the weapon’s damage die becomes a d8. If the attack deals damage, it can be Force damage or the weapon’s normal damage type (your choice).

Quote from VerilyRaze >>

 [...] True Strike does not require you make an attack roll as part of its casting [...]

 That an attack roll is made as part of True Strike is already explained in the 2024 SAC:

However, an attack made as part of True Strike works with Sneak Attack so long as it fills the normal requirements for that feature. For example, if you have the Sneak Attack feature and cast True Strike with a Finesse weapon, you can deal Sneak Attack damage to the target of the attack if you have Advantage on the attack roll and hit.

Quote from VerilyRaze >>

[...] There is no attack roll made during the casting of weapon cantrips like Booming/Green Flame Blade or True Strike. [...]

 The 2014 SAC doesn't support that interpretation:

Introduced in the Sword Coast Adventurer’s Guide , the green-flame blade and booming blade spells pose a number of questions, because they each do something unusual: require you to make a melee attack with a weapon as part of the spell’s casting.

Quote from VerilyRaze >>

The distinction between keywords and plain text is a fairly important part of 2024 5E, not "hair splitting".

There are no examples of a spellcasting stat in 2024 5E that is not Int, Wis, or Cha. More importantly, there is a distinction between the stat you use for spells - your spellcasting stat - and the stat you use for weapons - Strength or Dexterity. If an effect is using the stat used for weapons, it is a weapon attack rather than a spell attack. This distinction is why True Strike does not have any spell attack roll associated with it (and thus cannot be affected by purely spell-based abilities like Innate Sorcery).

True Strike does not require you make an attack roll as part of its casting. It requires you make an attack roll as part of its resolution. There is no attack roll made during the casting of weapon cantrips like Booming/Green Flame Blade or True Strike. Only once they resolve are you granted a weapon attack which requires a weapon attack roll.

 so by this thinking Firebolt isn't giving you an attack roll as part of its casting, but its also giving you an attack roll as part of its resolution.
Sorry this is splitting hairs, for me its a clear cut True Strike makes an attack as part of its casting => meaning innate sorcery works on it

in my view, it is a weapon attack enhanced by a spell and innate sorcery applies since it applies to spells. however, i adjust to the DM rather than argue because i got some other nasty shit in the queue if they want to be like that ;-) (i.e. silvery barbs on ring of spell storing for starters)

I wonder what is the consensus on what counter spell would do? 
For example, i use innate sorcery to get advantage on the attack (roll 11 and 13) with my crossbow and it is a hit (AC 18) because my Spell casting modifier (SCM) is +5.  If it is counter spelled, then innate sorcery does not apply and neither does my SCM bonus so we use Dex which makes +3 to hit and is now a miss.  But lets say my Dex is +3 so a +5 to hit...oh wait...which was my first roll?...so 11+5<18...miss.  right?

Quote from sdyvn >>

I wonder what is the consensus on what counter spell would do? 
For example, i use innate sorcery to get advantage on the attack (roll 11 and 13) with my crossbow and it is a hit (AC 18) because my Spell casting modifier (SCM) is +5.  If it is counter spelled, then innate sorcery does not apply and neither does my SCM bonus so we use Dex which makes +3 to hit and is now a miss.  But lets say my Dex is +3 so a +5 to hit...oh wait...which was my first roll?...so 11+5<18...miss.  right?

 If the spell is countered, no attack happens. True strike isn't separate from the attack.

A better question would be: what happens if I use True Strike on a Rakshasa? If you're claiming that True Strike is a spell attack, it would automatically miss. If you're saying that True Strike merely grants you a modified weapon attack, Greater Magic Resistance would not apply.

Rules Glossary: "Spell Attack"

"A spell attack is an attack roll made as part of a spell or another magical effect."

True Strike requires you to make an attack roll as part of the spell. True Strike is a Spell Attack.

Rules Glossary: "Weapon Attack"

"A weapon attack is an attack roll made with a weapon".

True Strike requires you make an attack roll with a weapon. True Strike is a Weapon Attack.

I cannot see anything in the PHB that says an attack roll cannot be both.

Innate Sorcery

"You have Advantage on the attack rolls of Sorcerer spells you cast."

True Strike is a Sorcerer spell that uses an attack roll so it qualifies for Innate Sorcery advantage regardless of whether it is a spell attack or weapon attack or both.

Magic Items

Anything that increases Spell Attacks would apply to True Strike, such as the +2 from Robe of the Archmagi.
Anything that increases Weapon Attacks would apply to True Strike such as the weapon magic bonus (the +1, +2, +3).

A staff of Power wielded by somebody wearing a Robe of Archmagi and using True Strike would have +6 bonus to hit (robe spell attack bonus, staff spell attack bonus, staff +2 magic bonus). With +5 Charisma and +6 proficiency this can be +17 to hit.

This does seem like an oversight but does seem RAW to me. However, given this requires specific end-game magic items then it's pathetically trivial compared to the "destroy a town" and "warp reality" level things a Sorc can already do by this point. And the cantrip won't do anything at all against the various enemies able to nullify magic in some way (rakshasa, beholder, astral dreadnaught, anything with antimagic field or similar). Even the max stat with boosts is only on-par with some of the BBEGs type monsters and with less damage output.

So whether this was intended or an oversight - doesn't seem like a big deal either way. ¯\_(ツ)_/¯ Cool, strong, but not even close to being game-breaking.