ALL questions on Khan are official LSAT questions created by LSAC. They do include questions from PTs that haven't been released, so you won't be able to find them anywhere. No questions on Khan are fake/unofficial.
Thanks for the response! So I did a diagnostic on Kahn Academy a few days ago and scored a 156. I would like to do it again to get more personalized recommendations here, are you referring to the test from 2007 in the curriculum?