Don't all minor league hockey require visors anyways? I've never seen a rookie player outside of 4th liners who don't wear visors.
I think you're right, the minors it might be mandatory. But what tends to happen is these guys get up to the NHL and out of pressure remove the visor to fit in basically.
I don't remember who it was on the Leafs this season, he always wore a visor in the minors came up and took it off one game and got hit in the face with a puck or stick, immediately put it back on.