[The STE]

Freddy vs. Jason never really happened (within the cannon of the story. Obviously it never REALLY happened). The whole thing was Jason in hell. He was killing because of his mother, not because he got a kick out of it. If not for her and the events of the first F13 movie, he wouldn't be killing anybody. So he goes to hell and ends up having to kill for someone else and is basically powerless to fight against it.

Either that or it did happen, and Jason was given a more tangible, waking hell. Remember, Freddy apparently became some kinda demon (or was always a demon if FvsJ is going by the New Nightmare cannon) so it's not out of the question that he'd have some power in hell.