If O'Sensei himself had a weakness, a something he had yet to improve and learn, it was how to communicate (teach) the principles he knew in such a way that others could understand and grasp.
Doesn't O-sensei mean Great teacher?
As far as Tohei sensei goes, my opinion is that those 4 principles Tohei sensei describes are much better thought of as "principles of validation" than "principles of implementation".
I have experienced so many people trying to "extend ki" in a way that is just stupid in terms of martial arts. If he said something like: "expand intent in six directions all at once such that you are able to support the spirals you create while engaged with attacks" - it would be a bit more helpful to me...