It would be a potentially breaking change so out of an abundance of caution likely would require (or need to wait for) a new version of HTTP like HTTP/4.0. On the other hand, adding an entirely new Method potentially can be applied across HTTP versions. It's possible for an HTTP/1.1 server to accept QUERY today under this RFC, it doesn't need to wait for and upgrade to HTTP/4.0 service, whatever that would entail. (Especially in the Postel's Law world where HTTP/1.1, HTTP/2.0, and HTTP/3.0 are all living side-by-side and are very different protocols under the hood.)