Well, ghosts in particular can be problematic because in China very often ghost stories have contained deeper, potentially political, meanings.
Also, these movies you refer to, what kind are they? I’m under the impression that in mainland China, a filmmaker might could work in a little bit of the supernatural in a light, fantasy setting (or martial arts), but it’s definitely not going to be permitted in anything even remotely spooky. (Unless it’s all explained away, Scooby-Doo style at the end. I think that’s been gotten away with a bit.)
