Very true. Even if a sleeping monsters takes damage upon being poisoned, he will stay asleep for one turn no matter what. If he doesn’t take damage, I get him staying asleep. But if he does, then staying asleep is a bug.
Another sleeping related issue (which I’ve only seen in pvp, but several times there) is if a “dreamy entrance” monster comes in and dreamy entrance hits the next monster in line, that monster will appear asleep but will actually get to do one turn. Obviously a bug.