The thing is, nowadays games tend to use the DLC gimmick to make people purchase pre-orders, at least for multiplayers. So for a single player game, either they include some physical item to justify the preorder, or else there's no point in getting it.
At the very least, we know any bonus that comes with it isn't going to be some shitty DLC that you won't bother to use once the hype wears off...