Oh, interesting. Is that the only difference?

How often people actually do a hard refresh? I would guess most people don't know about that key combination.

not only that, but even when you have a resource with a long cache time, and cache-control public, the browser will still do a request for the file headers (a conditional request - one that serves the content if it has changed/doesn't match what the browser expects)

so an immutable resource wouldn't even need that request