HTTP URLs and HTTP methods are two very different things, somewhat conflated in that the browser treats URLs in the URL bar as a shorthand for generating a GET. While URL encodings are well standardized for general use in RFCs the parsing into an HTTP GET when entered into the URL bar is not, it's just good UI. The same would be said about the QUERY method standard, it's not about describing how the browser UI should allow making such a request header just what a valid one is.