IfCould there be a possibility that there really is something "hidden" in a Japanese martial art? That what was shown and taught to most was not the "full" art? And could it be possible that there is a specific internal body skill, aiki, that wasn't taught to many? If there is that possibility, then isn't it also likely that all the techniques taught to the masses did not have that secret?
It is an interesting question that you asked. While I can only point to articles and interviews as research material, they are, after all, secondhand information. Why did Takeda and Ueshiba teach techniques?
Because techniques are only the expression of your strategy and your tactics
What makes you a good horseman is not the number of way to use the reins, it is your ability to recognise situations and use the appropriate reins effect.
I am not sure there is secrets as in the medieval “vergorgen ringen” that you are not supposed to show in public.
Techniques are only defined by their range of applicability and I think the “what to use when so that you still have options” is what is not shown in most JMA.
If you take medieval fencing, wrestling, they do present techniques as well but they tell you as well which one you should use as an opening gambit inLike the breaking of the guards, or a Zornhau, streichen, or deflections from the krump if he attacks you in the zu fechten
Or the 3 wrestling from which “many wrestling, murder strike and bone breaker comes from”
And if you can not get the 1st wrestling, you can usually get the 2nd and if you can not get either you will have the 3rd.
As well they do make a difference between the getting in to proper range to fence (or fencing over extended); ie zu fechten
and the fencing from proper range; ie fechten
It is the same for wrestling, you have "zu lauffen ringen", the running wrestling when people rush you or at leastr a step to get you.
"ringen"wrestling from clinching, jabbing range and "auf ston" when a clinch is mutually neutralizing.
Last but not least, they do explain quite clearly the notion of relative timing with the notion of vor (before) nach (after) and indess (in the instant) at the movement.
All that represent a state more that representation of time.
To be in the “before” you strike needs to hit him before his counter can reach you and to stop it he must parry. I.e. he can void/dodge, you do not have the Vor.
So in the manual you do have the fundamentals strategy/tactics, how put that in action according to the initial situation/ context and techniques which can be chained together so that you stay true to the fundamental principles.
I think in most JMA that part is left to the individual or more realistically orally transmitted.