But I agree with your skepticism regarding graves vs sites. I seriously doubt the folks who were buried or did the burying expected or wanted the remains exhumed for any purpose whatsoever.
Native Americans clearly considered this kind of thing grave robbing (https://en.wikipedia.org/wiki/Native_American_Graves_Protect...). I can't see a substantial difference here.
I'm not sure where the line is. It seems like there should be a substantial benefit beyond just satisfying curiosity.