There is indeed a mathematical question here...
The xp tables shows that we need more and more xp to reach new levels (at least till level 11), but the reward to kill higher CR monsters increases as well (although not in the same proportions).
If BG3 followed the rules of d&d progression & reward, we would surely have a problem here : if BG3 was a classical TTRPG following strictly d&d5 rules, and assuming EA is just a small chunk of the game (25-30 % ?) we would end up the game at level (veeery high).
The trick here is that the xp rewards are nerfed.
Example :
* killing a bulette grants x250 XP when defeated in BG3 / however, this is normally a CR5 creature and should bring x450 XP
* cambion : x90 XP VS x450 XP
* redcap : x50 XP vs x175 XP
Etc, etc.
So Larian may drive this xp/level boat just as they wish by completely changing xp rewards, what they do.
It means that there could be a huge game with many many many fights, and they could just stop at level 12.
However, as we might face enemies of CR17 at least (adult red dragons), and probably more, I think a level cap of 14 at least would better fit than 12 (unless we have to solve bosses encounter with powder barrels).
