the fastness is an illusion, the piano rolls are sped up
(a while back the famous "Miss Texas plays Chopin scherzo" or whatever, proved to be just such a thing).
I don't entirely understand the piano roll thing. How do they record it? I read somewhere that they have to guess the speed of the performance but they can read dynamics and some nuances.
Personal touch, special artistic aura, art of pedaling, or simply rhythmic stabilty--everything left outside.