Outside of the formula of 1) rabbit chews on it and makes it sharp and/or 2) rabbit chews on it and makes a hole, large enough to get stuck, I think the other way this hay rack would be dangerous is if there wasn't enough hay in it/there was enough room that a rabbit would try to shove its head into a hole in order to get hay inside.
If your rabbit's head is large, I don't think it'd be that unsafe. All hay racks generally come with the same safety precautions, so check to see if your rabbit tries to get inside it and see how large the openings are in proportion to your rabbit's body. It's always good to ask about these things!