True that, the info about movements being too small, etc... I think I was on a bit of a rant, and citing an example (involving advice from instructors that is observably in complete contradiction to what we know to be true about the body) more than a general idea, aha. Along with that, a lot of the mental work in piano that changes our perception on playing is also quite invisible, and can be rather challenging to teach in a way that the student will understand. I guess what I was going for was that there is so much knowledge in psychology, physics, etc... that is just evidently ignored by so many instructors. The information they give can often be helpful, depending on how it's perceived, but it also can amount to a lot of confusion and misunderstanding.