Indeed, that's not a query string! The #, and following text, is a fragment, is client-side only, and isn't the subject of the blogpost. Neither is percent encoding, which is just another way to send the exact same path from your browser to the server.

Note that it has nothing to do with the length of the URL. That's just the error message he's chosen to use, because "4xx stop pissing about with my URLs" doesn't exist in the spec.