If Rob or Mike Sigman see this thread perhaps they could contribute more, but it's an interesting question where the Yoseikan Budo founder's son learned this movement, and what differences there may be in the Yoseikan world.
Dan, there's a certain logic to this stuff that's difficult to go outside of, once you're in it. Trying quickly to think of some analogy that will allow me to toss in a meaningful but short comment, let me try this:
Imagine one of those snap-together flexible support-poles that form the outside through-the-loops structure of many lightweight portable tents nowadays. About 9-feet long, I guess. If you line that pole up against an incoming force correctly, you can keep the incoming force at a distance.... but consider that only a "pole skill" used to strengthen the pole and not something you would really do as a strategy or technique. That example is the equivalent of pretty much all of Tohei's and Ueshiba's "withstand a push" demonstrations that they did. They formed flexible "poles" throughout their body, starting from the ground, at their will.
Now take that same pole and put against, I dunno, a wall. You want to shake a wave
pulse down that pole while simultaneously timing a push straight down the pole so that the combined forces of the push and the wave arrive together for maximum power. You can see a couple of problems, I'm sure, but the main problem is that if you concentrate too much on "making a wave" and neglect to keep the tip of the pole against the wall (or aimed at it), you'll blow the objective. A "wave" that is not focused along a connected, flexible, a focused path will simply be a "wave" (as cool as it sounds) and won't be particularly powerful. To do it correctly takes a path from the ground, a trained connection, and a wave-path that is focused along the path from the ground to the target. You can't just think "I'll hit him with a wave and that will knock his socks off"... it takes some knowledge (usually needs to be shown) and some training. And yeah, variations of this skill are found in a great number of Asian martial arts, but in my experience, that's a reasonable general description.