Are you sure those people said those things, and that you really understand what they said?
Why do you believe there is any way for you to know what Takeda, Ueshiba, etc were training in private, not teaching to most students, or hiding in plain sight?
a. Because it all fits into the nature of this work; practiced, discussed and disseminated for ages.
b. They said it...because it happens to be true.
I know people keep trying to make their own guy some sort of hero and unique genius. But they were all just playing with information that spanned generations and cultures.
Solo training was king for eons. Why...do so many of the high level arts, do solo training? The idea of cancellation and neutralization of force begin inside you, not outside of you. And the changing of the inside has a dramatic effect on the outside.
If you try and throw a large statue by pulling; you will eventually be pulled off your feet -toward the statue.
If you try to push on the statue, you will eventually be pushed back off your feet -away from the statue.
The statue did nothing but be a statue.
Manipulation of forces
Now, what if the statue had soft tissue and could play with it's own forces inside of itself? What if it could then move while retaining all of -that- while in motion?
Anyone attempting to play with it...would be screwed until they became like it.
Solo training is irrefutably important.
Remember Sagawa admitted to lying to his own students about it for 50 years.
Sagawa also did not want his book-explaining why aiki was about changing the body-translated into English!!
Takeda said never teach white people and NEVER talk about solo training
Ueshiba never explained why he was doing certain exercises, yet all of his descriptions were the result of internal training. In fact many of his doka were quotes of Koryu and Chinese Internal training models.
Daito ryu has a public history of stating that you should only teach one or two people
The body must change and the source of Aiki was never in waza, never in blending, or external tenkan. It is not a coincidence that those who state such things were amazing, and felt different than everyone else. They focused on solo training and the classic models and ... weirdly....strangely...they feel different and were famous.
The hard part for all of us was being misled. I am not going to argue whether it was on purpose or not, through ignorance or not. The plain facts are that the vast majority of people in the great Ocean of budo are all more or less average people trying to do things and work things that in the end...well...make them feel no different than from the day they started. As shihan they are plagued with the same issues as a shodan; too much muscle, too much shoulder, moving from the hips, too tight, one side weighted, moving disconnected and offing themselves under load, or tensing up against resistance, not having any real explanation for what moving from the center really means and what a dantian even is, and end up having a structure and a body that was custom designed and tailored made.... to be thrown by virtually every budo principle known to man.
That..in itself is very revealing. Most of these principles came from Asia. And yet here we are....practicing Asian arts with Asians... and we end up custom made to be thrown by them with no idea, no teaching, of how and why we can blow all of those principles up, just by changing our own bodies!!!
I have no intention of spending the next twenty years trying to feel like your average Tom Dick and Harry. It just doesn't seem like a smart idea to me. I am going to continue to pursue the aiki that is a balance of in/yo in me, just like Ueshiba said to do.