We've probably reached a point where we might as well agree to disagree ...
To learn to retouch at a higher level How do I get... must be preceded by Why should I?
Must? I would say might be preceded. There's no pedagogical reason why a person can't learn techniques first and later gain insight and judgment about using those techniques. Children learn to stack blocks before they learn how to build cathedrals.
Principle based learning vs. Technique based learning.
Neither principle nor technique is pre-ordained as a "basis" for learning. One can readily move from one to the other, and back again, in shuttle fashion.
You are always there to provide the technique and unless they understand the principle behind what you did, than they will always be dependent on who ever showed them the technique. Namely you.
Always? That's a very sweeping empirical generalization. Are you sure you have the empirical evidence to support it? (I'm pretty sure you don't. You're making stuff up.)
Off course for full sucess you need both principle (why does it work) and the technique (how dose it work) to enforce that principle, otherwise its just a theory. But order of questions makes a lot of difference.
As I said, we can just agree to disagree about this. I would only point out how often you insert absolutes into your answers: must, always, never.
You seem to assume that when people ask, "How do I get this effect?" they are only going to paint by the numbers. I make no such assumption. They might follow the recipe like blind mice, or they might use it to achieve something brilliantly creative. I have no way of knowing and no need to know. When they ask a specific question, I give a specific answer. I make no guesses or assumptions about what they'll do with it -- or what they're capable of doing with it.