If you find games that claim to run on more operating systems than they actually support, please report them (as miscategorized) so staff can fix the metadata. That said, it's a good point. Maybe we could use a dedicated rubric in metadata, if it didn't mean even more fields to fill in.
Funny story: I once had the opposite problem, when someone running Win64 couldn't run my game made for Win32 and I didn't know how to help. (Not having Windows, my builds are tested in Wine.) Turned out there's a compatibility mode you have to enable, but that was very close to being a refund.