Agreed. And there are exactly zero clients I know of that actually support all the variations. With rare exceptions, even p-mutes are restricted to either public or private, at least when it comes to writing. (Reading is a bit better; a lot of clients can handle it).
NIP-51 really needs a reality check. Kind 10000 and 30007 are just two of many, many things I struggle to find a good reference implementation for.
From a relay perspective, you wouldn’t believe how much junk those lists contain, and how much clients spam them. I have some generous rate limits to my relays, but as soon as I open certain clients I know that they will reach rate limits in seconds reading 10000, kind 10002, etc. Even on personal relays 🤣.