I don't believe there is such a thing in real life as "perfect" piano practice either. Everyone has different needs in different areas of piano that they would need different approaches to overcome. That original post of mine just described a basic core idea that should be a solid guideline for getting more efficient at it, but without specific details and choices each one would make. If this was all there is to it, then piano instructors would be obsolete, and they are far from. Even top tier pianists occasionally take lessons from others.

Compared to other skill-learning experiences that require practice that I had, I don't think piano is in its own separate category, it is very similar to pretty much everything else. I simply picked it because piano makes it easier to illustrate that principle to the general audience. Same thing can be said about sports, visual arts, etc., anything that requires work through repetition, heavy knowledge/experience, and is heavily-reliable on manual execution with a very high (nearly infinite) skill-ceiling (i.e., not something like writing software where knowledge is about 95% of the work, execution is about 5%, since execution is literally just typing and knowing your IDE shortcuts, both of which have a fairly low skill ceiling).