That's just a way to spell out the HTTP 2 request-line (its http/1 equivalent would be the very first line of the request like `GET / HTTP/1.0`) in human-readab

That's just a way to spell out the HTTP 2 request-line (its http/1 equivalent would be the very first line of the request like `GET / HTTP/1.0`) in human-readable form. No parser is ever going to parse these strings. HTTP2 supporting libraries see the well-known binary values and libraries without support for HTTP2 will fall-back to HTTP1 anyways where the human-readable form of the request-line is, well, just the request line itself.