The question is posed "So are we back to "Hidden Moves" inside kata discussion/argument? Where the masters only showed these to their favored students? "
We need to make some fine distinctions here for intelligent conversation.
I have experienced several different versions of this training, to understand that not only one approach to training is being discussed.
In each case being a student was not a democracy, where their wished had any impact on what the student wanted.
First, there is the traditional program that the instructor experienced himself, and that training was taught in a specific order. There his instructor did not discuss what was available with students before they reached a designated lever in their training. Most likely that was how they too were taught.
So someone in that tradition would not share information until the student qualified for that level of training. They are secrets in the sense that they were never discussed until the appropriate levels of training were reached. And that may have involved decades of training.
Next is the traditional instructor who shared some knowledge, but then the student choose not to work and master that knowledge. In return the instructor would choose not to share more knowledge.
I am thinking of one instructor I know who often taught a kobudo kata to a student, then in time the student decided there were more interested in another weapon, and stopped practicing what they were originally shown. And they were not shown anything more. As they failed the test, they were not even informed what the test was, it being their dedication to the way the instructor shared the system. In this case any time a student choose to find another way, that disqualified them from other training. Not fair, but the way they were taught.
Another answer is that the student is never shown information before they have trained to the point they are ready for that information. So hidden secrets are just that, information that one is not ready for in that system of teaching.
It is not impossible to understand if that is the way the instructors instructor taught them. Then they are simply keeping a tradition alive.
Of course today with so much information being exchanged, the idea offends some. Then again who is to say that it is not right to offend them?
A different sort of instructor is one who worked themselves to understand how kata applications could be used. When you experience such an instructor, most times they are so focused they cannot stop sharing what they are continually discovering.
But at the same time there are no secrets to what they show. If you experience what they have via a clinic. That is almost the same as getting nothing. For every potential application builds forward. Without the one to one experience, you will unlikely really get what you have been shown.
One very traditional instructor I experienced, explained that his father would be called on for ‘secrets’ when he would give a clinic. He never hid anything, gave them the full technique series. Knowing no one present would actually retain it, except where they were actually at the level to ‘get it’. Otherwise it became ‘vapor ware’ or ‘ the technique of no technique’. I have experienced that from various instructors from different cultures.
Knowledge involves work sweat equity. Not casual discussion. There are layers and layers of understanding. Just wanting simple answers is rarely that you will understand what is shown.