that was the original plan
the game was originally going to have Tails, Knuckles and Shadow as playables, but then the vocal and unpleasable fanbase said they wanted it to be a "Sonic only" title, so Sega removed Knuckles model and converted all the unfinished gameplay that they had developed for him into the "werehog"
the games Original title was gonna be Sonic "world Adventure"(and still was in Japan) meaning it was basically originally Sonic Adventure 3