My thoughts:

Having a father went to Italy to study concert piano -- I have to say that there arm movements. To what degree? I think it may have a lot to do with volume -- accenting

When I am trying to improve my finger technics I do scales and arps on the piano. Returning to the keyboard I seem to have more command. Studies start slow an accurate, then gradually speed up.

I use an acoustic guitar which has high action in the same way. Returning to a guitar with low action I can breeze through the same piece of music.

John C.