Hardness of paint and scratch resistance are two very different things. One involves the abrading and leveling of the paint, the other is cutting into it. Think about cutting a "scratch" into a stick of butter and a piece of steak. With a good, sharp knife it's pretty easy to do both. I'm not talking about cutting through either one of them, just cutting a little tiny bit into them.

Now try to make both of them level again by lightly dragging a non serrated butter knife across the surface. It's ridiculously easy with the stick of butter, but I defy you to do it with the steak.