No time for a lengthy post...got to go train all day.
Yes, Asagao is not a simple hand movement thing, it is a body principle involving dantian, elbow power and fure Aiki. Though I imagine just about everyone learned it and sees it ads a hand movement!!
As for the Japanese way of teaching....Sometimes it's fascinating to see profound things being reduced to an obvious movements and people think what they see is all there is to it. I have no opinion on why they do what they do. My choice is to explain them and actually teach people to do these things.