Yeah, well they gave us Berserker Barbarian which is not in the PHB sooo they clearly aren't sticking strictly to the PHB... They also gave us Drow and Githyanki which aren't playable races in the PHB
Berserker Barbarian is in the PHB, although Larian has made changes to the class similar to what they did for the Ranger (both are widely disliked/thought to be underpowered RAW). Compared to the RAW Berserker, BG3 removes the Level of Exhaustion penalty for going into a Frenzy and adds the option to Enraged Throw instead of making a Bonus Action Frenzied Strike.
"Dark Elf (Drow)" is also a playable race in the PHB, as a subrace of Elves.
But yeah, Larian has added stuff that isn't in the PHB: Githyanki at the very least, and probably more I can't think of. And these forums are certainly the right place to advocate for adding races/classes/spells from later books. Booming Blade in particular seems right up Larian's alley; its conditional effect is similar to BG3's magic items.
