I have a friend who worked for Ducati Corse for a while, so I asked him what they use for the air filter on the MotoGP bikes. He replied, "...up until 2007 (but I think they keep doing this) we put a small K&N type (can't remember if it was a K&N or something really close) filter; I remember that the element between the mesh was really really thin, almost paper thin, especially compared to the ones you can find in the shop. Another team member and I had a small puzzling moment whether it was just a fine metallic mesh or if there was something in between, but we then both agreed that, again, it looked like a K&N as described if not a real K&N."
FWIW, I have never been a fan of K&N filters but I figured that this bike will never see really high miles. (I have >100,000 miles on my regular street bike and it uses a single layer of open-cell oiled foam for a filter.) I had my air box and throttle bodies off when I was working to fix my hanging-throttle problem and they were quite clean. So I am not going to worry about it.
Your Mileage (or filter experiences) May Vary.