Explaining every plot hole as the tadpole, the tadpole, the tadpole gets so lazy and unimaginative after a certain point.
So much rests on this tadpole for the story. What happens when we inevitably remove it before the end of the game?
And yes, it would mean the Drow are gimp on the surface but the best underground. That's how it should be.
Humans are still penalized by lack of darkvision elsewhere with no option for something like the tadpole giving them darkvision. I don't understand how hard it is for them to pay attention to balance.