As someone who makes knives and swords as a hobby, I can verify that many things are capable of sharpening iron. Slightly less things are capable of sharpening steel.
Know what's great at refining a dull edge to be razor sharp? Ceramic. And I have legitimately heard someone refer to ceramic safety box cutters as "woke" at work. I don't get the (il)logic of that...
So uhhhh.... Yeah. Even "softer" things will sharpen stuff.