At no point is the cause of death stated for all ghosts, the edibility of enemies does not change, neither does befriendability.
The point of it was also stated already.
Not sure what you mean by omitting items.
The saferoom ghosts and two others implied that the spirits were all eaten since they tell japes they'll end up like them, and a couple of the game over screens showed Japes as a ghost; made me think all the ghosts were eaten. Can't imagine someone else wouldn't get that idea. Might want to establish that not all of the ghosts were eaten. Reminds me of a certain 1cc'r that made a witch but specifically didn't want her submissive.
What I mean by omitting items is giving the player an alternate option to destroy them or do something to prevent them from showing up on future floors for the save file.