I played piano competitively in college and when my teacher revealed a version of this trick for memorization it seemed like a cheat code at the time. Playing a short difficult motif over and over again is needed sometimes to get it right, and the key was to lock in the “correct” movements and not retain anything else. So the idea was after you played it once correctly you would take a moment and let the section recede from short term memory and hopefully into longer term storage and then start practicing again.