Also, an illithid with their host's mind and memories completely still intact is the greatest fear of the race because of a legend about a creature called "The Adversary" so even those illithids with even small telltale signs of their former host, like wistiling a tune the host used to like in it's life before the ceremorphosis, go to great effort hiding those traits as to not be killed by its peers.
So even if technically the story in BG3 could be about this legend, I find it farstretched.
Maybe the Absolute and the Adversary are one and the same person?
