Are people trying to say that Schumann didn't foresee this kind of speed actually being possible?
I think he did, all those markings like "as fast as possible" and then "faster still", which I believe are in the last mvt. of this sonata, and also the frightening abundance of difficult figurations throughout his early piano music. Like Liszt and Chopin, he was set on creating a new transcendental piano technique, inspired by Paganini. But he wanted it to be expressive and beautiful, and Ms. Kim for all her speed, energy, mech and fury is utterly lacking in this aspect of the music. Schumann's music is literally bipolar, it veers between extremes of fast violence and almost free tempo fluffy cloud music, if you will. (Florestan and Eusebius, his literary and musical alter egos).
Glad you like Schumann now. Now you should listen to Richter's and Lazar Berman's recordings of this piece, if you haven't already....