Not quite. Half-illithid is any non-human humanoid. That is:
Human + tadpole = illithid
Other humanoid + tadpole = half-illithid
Anything else + tadpole = dead
Except LoM specifically states that illithids' favorite victims for the procedure are drow.
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Originally Posted by Xuincherguixe
... that works really well, it's almost like...
Oh god! Chuck Norris is Cthulhu! It all makes sense now. Everything is meaningless! Only in death can we escape!