Drakthyr canonically are supposed to be learning new stuff from Mortals. That has been the line since DF launched. That is what the patch notes confirm.
So why are the Drakthyr suddenly being presented as just waking up as warlocks and shadow priests? It makes no sense.
They cant make dracthyr other classes cause of the extra utility they bring.
It is true that there is a lore inconsistency there with the reason they describe for them being able to be other classes and the way they are presented in-game. Imo instead of having them just awake in their creches they instead should have been students of the Algeth’ar Academy fresh from training and moving on to their selected faction city