Nonsense

Yeah but there's some plausible deniability when it's called the "fast lane" because some will think "oh I'm already going as fast as the law says I can (or faster), therefore I don't need to worry about those people going even faster than that because that's illegal".

Calling it the passing lane would throw away that argument because the speed and legality of that speed no longer matter: it's all about going faster than those on the right so they can be passed, not how fast one should be legally able to go.