I still think alien parasites in your brain is just disgusting.
Roleplay-wise 99% of sane characters would want that thing out of their head asap. And the game just won't let you. Larian decided
you will use our fun powers. This is an RPG, not a platform game where you collect fun powers and story doesn't matter.
You don't need the tadpoles for plot device beyond Act I, after you have joined forces with unlikely allies and learned what's going on. After that, becoming a hero or a villain in the events of the game is motivation enough. They should have offered a way to extract the tadpole at this point.
And it just gets worse and worse when the emperor starts broadcasting in your head. Probably the Ring of Mind Shielding I've always been wearing is just a pointless trap item at this point, too.
So yeah, it does smell like gameplay devs calling the shots again and wanting those powers for all players, panicking last minute about late game not having enough progression.