What is being shown in this video, all be it very well, is a simple demonstration of structure. Now the fellow demonstrating it, Chen Xiaowang is clearly very physically able, and is very practiced at this method of body use. I wouldn't say that the average person could do what he's doing without a significant amount of training, probably around a year or two. However the principle that he is using in this demonstration can be achieved by any average person in only a few minutes, and you can show a similar feat against someone significantly larger than you as soon as you understand what I am about to write.
When the strong man pushes into Chen Xiaowang, Chen locks his arm under strongman's arm pit, joining their structures. Every time the strongman pushes he is actually pushing against himself via a very simple redirection done by Chen Xiaowang. Here is a diagram to help you understand this principle.
Because of the simple redirection, every time the strongman pushes (force "A"), that force goes through Chen Xiaowang's structure, and back into the strongman (force "AB"), pushing the strongman up and back, and Xiaowang's structure down every time he pushes.
yes, it is a demonstration of structure along with several other things and I agree that what he demonstrated can be done by anyone and probably in a shorter amount of time than even what you gave, if they practiced and did the necessary conditioning, but I don't understand how what you're describing works in the way that you're describing it. How is this push into his upper chest/shoulders mechanically traveling around through his arms and back to the strongman. How does that work? You describe it as a mechanical process, but I don't see the mechanics. How is the force/push conveyed back to him?
I modified your image as I see it:
What I see is CXW simply relaxing and letting this man push him into the ground. He's providing no resistance and not letting any muscle tension block that force as it passes through him to the ground. CXW's center of gravity is effectively in his feet and his body is so well connected, it doesn't "give" as you or I would, so the push makes him heavier and can't throw off his base. The guy may as well be pushing down at an angle into his hip in an attempt to push him back, which is where the lack of traction and such comes from. IMO, it would be like you or I pushing down onto a big rock that's half buried in the ground rather than pushing at it from the side to move it. We're not going to move the rock by pushing it down into the ground, we're just going to make ourselves lighter and push ourselves away. He's also doing more behind the scenes in regards to force vectors and protecting his center and all that, but if we're that far apart on how we think he's doing what he's doing, there's no need to go there. On the surface everything he's doing is probably simpler than what even you were getting at, but more difficult at the same time. The hows are far more difficult than the whats.
I see no difference in what he's doing here than what I've seen of Ueshiba sitting, letting people push his head, or the jo trick or the pics of him pushing the tree. As Ikeda would say, "same, same". Do you agree or disagree?