As you know, I trained with John Stevens, but it was well after Shirata passed away. For me Shirata is like a shadow that I can perhaps get little glimpses of, and even then, I am not really sure what I saw. I envy the hands on time you had with him!
I've heard this before and I am convinced that it is impossible for John, I and others to relate our experience. For me the memory is immediate and palpably present. So, when I hear you and others say this I gain an appreciation for the frustration that my teacher (and certainly other students of O-sensei) felt when he tried relate to us what his experience with his teacher was like. One can try, but it is impossible. Hopefully a bit of "the magic" passes on student to student.