err..what?
I.e., we practice for security, and I don't think that extensive practicing (e.g., hundreds of repetitions) and depth of musicality are mutually exclusive. It is what is going through the mind while practicing that is important - not how many or how few reps. Schnabel's own son once attempted to reproach him for practicing mechanically, repeating a passage several hundred times, but the maestro's response was "Each time, I play it a little differently." Evidently the difference was too subtle for junior's ears, but not for those of the master himself.
I believe we are often too quick to assume that the pianist who repeats a passage over and over again is practicing mechanically. In order to be secure in performance, for many it is necessary with difficult passages, once having intellectually discovered the proper motions for them, to play them many times in order to engrave them in the muscle memory. The only way that the result will be unmusical is if the practicer is reading the New York Times during this process.
With regard to Slobone's initial statement, my conclusion is that the two pianists may have practiced just as much (let's remember Sokolov and Richter, both compulsive practicers, who achieve(d) magnificent results), though in one, the artistic musical gift is simply not the same, or the mind was not concentrated on the music during those practice hours.