We're explicitly told that our tadpoles are unique multiple times. All the normal rules of ceremorphosis are pretty much out the window. At the very start of the game we see a woman get transformed fully into a mind flayer with the pull of a lever, something Lae'zel notes as new and terrifying technology the Illithids shouldn't have.
Shoot, we don't even know for sure that ceremorphosis is even the end-goal of these tadpoles. They're connected to The Absolute which seems to be some sort of take over the world through manipulation scheme operating on a larger scale than simple reproduction.
We're dealing with unprecedented magic. Something the Mind Flayers have never attempted before with goals that aren't immediately obvious. There's no reason to out-of-hand discard the idea of a playable race based on old lore because this is new lore following its own, new rules.
Beyond that, how the heck would you justify them implanting a dang goblin with a tadpole but draw a hard line at kobolds? Because kobolds are skinnier? Seems like a pretty massive stretch without even knowing what these tadpoles are meant to do.
Last edited by SaurianDruid; 09/11/20 10:30 PM.