In the newest community update they refer to it as consuming the additional tadpoles which suggest something mor along the lines of us feeding them to the tadpole already in our brain...which if nothing else it is true that tadpoles eat other tadpoles...that is a thing that happens in illithid brine pools.
But then again their very own UI shows your additional tadpole "diving in" and carving a hole in your new unlocked talent.
