App rejections were silly pretty much right up until September of last year when they released more guidance - well over a year after he came back from medical leave.
Were he to quit tomorrow and never talk to an Apple employee again, we wouldn't see the damage done/advantage gained until at least 6 months, if not 12+. Product design and direction is set a long way before release, and though he might veto early products, I doubt anything hardware related within a 3/6 month window of release has ever been killed (nothing would have been allowed to get that far).