The other day one of my organ students played a piece for me. She claimed to have learned the piece.
And yes, she practiced it in small fragments, later put them together, stopping at 1 beat, 2 beats, 1 measure, 2 measures, 4 measures, 1 line, 2 lines, 4 lines, 1 page, 2 pages, 4 pages until she learned to play the piece without stopping.
But you see, she still made a lot of mistakes in front of me and her playing was, well, boring.
What happened? Is her practice method that I recommended not efficient?
I don't think so.
It's just she needs so much more to be able to convincingly play it in public.
She needs to have analyzed it (which not too many people like to do). She needs to notice while she plays what she has analyzed. And then she needs to be in the flow - keeping a steady focus while breathing deeply and fixing her and the listener's attention to what's going on right now.
All of it requires adequate time to prepare. All of it requires deliberate practice.
There's is so much more to music than playing the notes.