I think you could characterize it that way if you assume that the there is only one way to efficiently move and neither internal nor external movement is inherently different. The problem I see with that is that what is considered efficent for external movement, is not always considered efficent for internal movement because they move fundamentally differently. That is to say, there can be at least two ways of efficent movement, both of which have their tradeoffs.
Ok, we're getting at the heart of it with this post I believe.
So, if there was only one "best" way to move the body
, then we could say, Internal is the study of efficient movement, and External is the study of making a more powerful body.
We can agree on this, correct?
But then you are adding the caveat, that some believe there are other ways to move the body. And that there is likely a better way to move the body then professional athletes have found. So one must study efficient movement within this "better" way of moving the body to truly study internal. Am I understanding you correctly?
I think you have to differentiate technique from principle. Technique generally refers to one specific movement for a particular situation, such as a particular waza. Principle is generally how you power any particular waza. This is why I tend to state that a throw is the same as a kick, as a cut as a punch. It is a different focus in terms of how you practice.
I think this is a good distinction to make.
Techniques are specific methods used to achieve a specific goal.
Principles are inherent limitations and advantages within the human body.
If you think that is about what you are going for, I agree that this is a good and useful distinction.