We're still building out schemas, so I wouldn't rate the protocol based on the current number. I just didn't want to speculatively add a bunch without having the live system to test against.
If I thought any of the existing standards were winners, I would've gone with them. If you really want to get mad, you can read why I decided not to use RDF or JSON-LD: https://unwalled.garden/docs/why-not-rdf