It does look inconsistent. However, the head of the language lab, a male, may have received the data from one of his workers/researchers who could have been a female, namely the black kid’s mother. Thus, the mother discovered that the tape was English in reverse, informed the language lab boss, and the boss then told Karras. It’s a stretch, but not impossible.
Yeah it’s bad storytelling. Blatty really stretched alot of stuff in Legion. Kinderman and Karras were hardly friends yet each year Kinderman and Dyer mourn Karras’s death and somehow Kinderman has a picture of himself and Karras. Also have you noticed in the first film it was said that Merrin’s first exorcism lasted months and nearly killed him yet it last for maybe a day or two in the two prequels.
I don’t have a copy of the book in front of my so I’m just going on the movie…………..but……….Isn’t the person who discovers that Regan is not speaking in a different language but in backward English; isn’t he a man?
In Legion, it is stated that the boy murdered in the beginning of the story is the son of the woman who figured that out!