Hypermedia doesn't claim that you don't have to read the docs, that's a misconception. You do have to read and know how to parse the file formats.

The main advantage is that know that your application supports Twitter, it also supports every other service that uses the same file formats, since they can be shared, re-used and standardized. Obviously, two services can't use the same URLs, so if you hardcode them, you're locked in.