After making lots of parmesan I do have to kind of concure, it may not be "pressed" but they do use a weighted follower of, I'm guessing, 10-15 pounds. And my recipes call for only 20 pounds of pressing, but that's at a 4" wheel so for my wheels it's a lot more. Anyway what I concur on it that a lot of the hardness of parmesan comes from the high temp cooking where it releases a lot of whey so the curds go into the mold pretty hard anyway, hard compard to let say a cheddar.
P.S. Excellent links, thanks.