I don't think you have a clue about the relevant law if you're saying things like "derivative works are fair use". They absolutely aren't which is exactly the reason game devs can exert such strong control over mods generally. Fair use would not necessarily limit commercial use either if it applied here.

In the case of the VR mods they are making the argument that this is not really a derivative work of the games in question at all because it is a generic framework that supports numerous games similar to how an emulator runs all the games of a platform and can present them differently from the original hardware. We won't get to see how that argument would do in court probably because the modder can't afford to go to court with these huge companies.

I wouldn't really say it's about "property" either. Copyright and all these related rules are a completely man-made concepts unlike real property which has a pretty intuitive basis in our reality where only one person can hold a physical item at a time.