I seriously doubt that there's any debate about the value of practicing slowly. But I find it a little hard to believe that he "never" plays a whole piece in tempo. That sounds to me like he's saying the first time he does that is in a recital. I've read the passage a number of times, and I don't think I'm misunderstanding what is printed. No big deal, it obviously works for him, but I just found it a little odd. I wouldn't dream of playing for an audience without being absolutely certain I could play the tempo I want."The key is proper practice. I only practice slowly at home. I never play a whole piece in tempo. I use a metronome for practice and repeat every single phrase three to five times..."
Here's another passage which I found really illuminating. As in, a light bulb went on when I read it:
That really changed the way I've approached practicing in the few days, and the results are noticeable. I think I was trying to do what he points out, and succeeding to some degree, but slowing down and really paying attention to every single movement? I certainly will from now on!It is important to know exactly what the difference is between practicing and playing. Many people tell me they practice slowly but what they really do is play slowly. That is a completely different thing. You practice when you control every movement in your hands, when you take time for every shift, for every hand position change. You practice when you are in control of everything that is happening in your hands.