Never heard of him training with Dorian...
He did a workout with Dorian after the 1996 Mr Olympia for FLEX magazine, in which they trained back.
To the OP, Francois was 260 lb onstage a couple of times and when he won the 95 Arnold Classic, he weighed around 255 lb. So he was a lot closer to Jay size-wise.
He also had a much better back and conditioning, not to mention his best shape was as good as Jay's best shape (circa 2001), although they have different structures.