Again, not how Wayland protocol maturity works. All released protocols are versioned, and do not break existing clients. Servers offer a maximum version number

Again, not how Wayland protocol maturity works. All released protocols are versioned, and do not break existing clients. Servers offer a maximum version number for their protocols, and clients can request any version up until that maximum version. If they request an older version, the server will behave in accordance to the older specification. A staging protocol may end up being replaced and slowly deprecated, or have more breaking changes in new versions than you would find in a stable protocol, but a client using a particular protocol can rest assured that a server offering the protocol will adhere to the same version of the protocol contract the application was written against.