I don't know, but I imagine you would have to play excessively hard and long to get callouses from smooth, flat surfaces.
I admire you as a musician,
ted, and I don't doubt your experience, but are you sure about that?
Actually pounding on the piano, sure, like in rock and roll or something, you're going to get some loss of sensitivity in the nerves. Not calluses though, surely not.
But doing, say, octave work, especially if one doesn't have Eubie Blake-sized hands, you're going to be hitting, most likely, sort of the edges of certain fingers. Even if one has pretty large hands with no problem making the octave.
I could see calluses forming in that kind of way.
After all, it's just "rubbing the wrong way" against surfaces of varied geometry. Sort of like how one gets calluses on the feet, rubbing against the shoes, or walking barefoot across even relatively smooth asphalt or concrete.
I don't know about large, very rough calluses, but certainly some irritation from the repetitive rubbing action.