It is my belief that any interaction with O'Sensei was a teaching. A uchi deshi does not learn just on the mat.
Sure. But what did they learn? Did they learn the Secrets of Aiki, or did they learn that Ueshiba Sensei was a grumpy old man who was finicky about his bath?
The answer would have had as much to do with the temperament of the student as with the pedagogical skills of the teacher.
I took a course in grad school that was commonly described in student evaluations as "Fireside Chats with Prof. L." The professor sat at his desk and told stories. He rarely used the board. I think there was a textbook, but he rarely referred to it. The topic was ceramics engineering and the behavior of glasses. It was one of the most challenging courses of my life. Not because the material was difficult -- it wasn't, at least relative to something like quantum mechanics -- but because it was so difficult to extract tangible information from the lectures.
I'm also reminded of the scene in Jonathan Livingston Seagull where Jonathan is lecturing the young gulls about love and the Great Gull. But the young gulls are so exhausted from flying practice that they mostly just drift off to sleep.