You know, sometimes D&D RAW sucks:

Booming Blade

You brandish the weapon used in the spell’s casting and make a melee attack with it against one creature within 5 feet of you. On a hit, the target suffers the weapon attack’s normal effects and then becomes sheathed in booming energy until the start of your next turn. If the target willingly moves 5 feet or more before then, the target takes 1d8 thunder damage, and the spell ends.

and:

Green-flame Blade

You brandish the weapon used in the spell’s casting and make a melee attack with it against one creature within 5 feet of you. On a hit, the target suffers the weapon attack’s normal effects, and you can cause green fire to leap from the target to a different creature of your choice that you can see within 5 feet of it. The second creature takes fire damage equal to your spellcasting ability modifier.

Yep.

There's some chance that, if/when those two spells get revised for 5.24 (perhaps the new FR book coming soon), that might get tweaked.

Given that true strike doesn't have such a limitation, it seems pretty likely.

(It's also possible that they won't bother to update the two, as True Strike fills the basic need, and is much less fussy and more reliable in its damage.)

Also, there's nothing stopping you from just ignoring that limit. Bring them up to the modern template.