You will not turn into a mindflayer, that does not happen to true souls. Keep all the benefits of the tadpole.
I agree with you that this needs to be added, but currently this is simply not true. Everyone in the goblin camp thinks you are going to turn into a mindflayer. Gut imprisons you for it, Minthara does not reference it but has tons of other reasons to kill you anyway. Everyone is so hostile against their fellow "true soul", it makes the two novices that were with Eodwin showing up in the party a little ridiculous. "The Absolute brings people together" my ass, the Absolute just wants me dead apparently.