It is a vague policy that is ill defined. It's pixels and fiction. You could ban most Hollywood movies under such vague guidelines.
It's not "has x in it". That would be easy. Just like you can say, there's a nude pixel boob, it's nsfw.
It's something something gloryfication somethings something. Very ill defined. And morally highly questionable. There is games that glorify murder and genocide and slavery and other things, yet they are not under attack by the bigots.
So I would assume that the game in question might have x in it, but not in a way that violates guidelines. And from a legal standpoint, that's even more ridulous, since it is fiction and not illegal. Banning games is basically the same as burning books.
Oh, and the game is paid. Because of those bigot's attacks and blackmail, and because Itch has not implemented a sufficient solution to this, Itch hit an emergeny brake and just removed all nsfw games that accept payments from the public listings, so you can't find them within Itch by browsing.
Also, if it's "not allowed", it is not only not allowed to sell, but not allowed on the platform. The bigots have no legal grounds to try banning the content they do not like. That's why they pressure payment processors and those blackmail Itch. It's fiction for crying out loud. It is very, very hard to ban fiction. Even in prude USA. Especially in the USA. Fiction falls under free speech and even porn with actual humans doing a homevideo falls under this and is not legally bannable. That's why they fight so dirty. Inventing false arguments. Appealing to emotion and trying to invoke cancel culture.