War Caster let you use your reaction to cast a spell with a casting time of 1 action who target only that creature who provoke the opportunity attack..
This confuses me. If your argument contains “just because it doesn’t say” immediately means you are not speaking RAW but RAI or Rule of Cool.
Quicken specifically calls out the actual changing of casting time. War Caster does not so it doesn’t. It gives a specific rule that allows you to cast a spell with a “casting time of 1 Action” as a reaction. So you can Quicken BA cast Dissonant Whispers then, with War Caster Opportunity Attack, cast a 1 Action Cantrip. And use your action, if you wish, cast a 1 Action Cantrip.
Unfortunately it isn't that simple. The designers just aren't that careful with their wording of rules text. They made a choice to use "natural language" when writing the rules and to trust us players to not to be that picky when reading them (IMO a bad choice). The rules are littered with small inconsistencies in wording that aren't (usually) meant to have a substantively different end result.
On this issue we can look at two class features that have a slightly different wording, Meta magic and the Grave domain Cleric.
Quickened Spell says "When you cast a spell that has a casting time of 1 action, you can spend 2 sorcery points to change the casting time to 1 bonus action for this casting.". Grave Domain says "For you, it has a range of 30 feet, and you can cast it as a bonus action.".
Both features allow casting a spell that usually takes an Action to be cast using a Bonus Action but only one of them use the word "change", are we really to think that that difference in wording means that they have a substantially different working mechanic. I can't see that.
Of course the Grave Domain feature won't have the same issue as Warcaster has because you only have one Bonus Action but the principle is the same. When Warcaster says "you can use your reaction to cast a spell" there is no need to specify that the casting time is changed, the simple fact that it is cast with a different casting time than it normally would have been means that the casting has been changed.
Just to be clear, I would still probably allow Warcaster to do its thing because I don't think that the Bonus Action spell restriction was ever meant to target Warcaster, IMO it was meant to keep Quickened Spell from being way over powered at mid game levels.
It really is that simple. When you are talking about Rules As Written (RAW), if it is not literally in black and white (or whatever the color of the paper or screen) then it is not RAW. It does not matter the intent or natural language, it literally means if the words are not there then it isn’t RAW.
I can agree with you that maybe their intent or because of natural language WotC’s wording can be troublesome. But arguing intent then is outside of RAW discussion.
Maybe there is a reason they chose to use specific wording in one but different wording in another. I don’t know. Just like, as was previously mentioned, with unarmed strikes, a “melee weapon attack” and an “attack with a melee weapon” which in natural language means the same thing. But unarmed strikes qualifies for one but not the other. Wording matters, especially when talking about RAW. (And the difference was clarified in SAC for unarmed strikes)
Will this help? https://www.sageadvice.eu/could-you-use-war-caster-reaction-to-cast-an-action-cantrip-on-the-same-turn-you-cast-a-bonus-action-spell/
Its been already brought up in post #20
War Caster let you use your reaction to cast a spell with a casting time of 1 action who target only that creature who provoke the opportunity attack..
It really is that simple. When you are talking about Rules As Written (RAW), if it is not literally in black and white (or whatever the color of the paper or screen) then it is not RAW. It does not matter the intent or natural language, it literally means if the words are not there then it isn’t RAW.
I can agree with you that maybe their intent or because of natural language WotC’s wording can be troublesome. But arguing intent then is outside of RAW discussion.
Maybe there is a reason they chose to use specific wording in one but different wording in another. I don’t know. Just like, as was previously mentioned, with unarmed strikes, a “melee weapon attack” and an “attack with a melee weapon” which in natural language means the same thing. But unarmed strikes qualifies for one but not the other. Wording matters, especially when talking about RAW. (And the difference was clarified in SAC for unarmed strikes)
EZD6 by DM Scotty
https://www.drivethrurpg.com/en/product/397599/EZD6-Core-Rulebook?