Of course, sometimes the language isn't always there to describe what is going on. For example - when Ikeda Sensei is showing something (say taking balance from a same-side grab) very carefully, he will stand facing his partner so the grab happens on his center line. But sometimes he faces the line of students so that his arm is out at his side along with his uke. The action is way off his center line, yet he is just as successful. Over dinner, I asked him how he did it and he said, 'just put your center in your hand.' I can see that he does that and I've felt him do it to me. I'm still trying to figure out how to do it myself, though.....
I'd have to see it before I'd want to make a more explicit guess, Garth. Is there a video anywhere?
Generally speaking the outline of basic requirements for most of the demo's I've seen Ikeda Sensei do is going to be the same that I pointed out before:
*Ikeda Sensei must have a good contact with the ground that allows him to draw his power from.
*Uke's push or other contact must allow for the joining of the two of them as a unit (even if the direction of full unity is fairly narrow and forces Nage to act only along a limited angle).
*Ikeda sensei becomes one-half of a unit-structure so he becomes the controlling half and Uke's center, etc., just becomes something attached to him like, say, a backpack.
*Instead of moving his arms and shoulders to initiate force, Ikeda Sensei shifts the movement and initiation area to his middle (needs to be practiced and shown how to optimize it).
If Ikeda Sensei is truly offline from the force input of Uke then he has to be using his body connection as a factor added to the above steps. To do that well you need to be shown how to train, so that's a little outside of the basic how-to's that are easily discussable on the internet. The classic "well-trained body connection" trick is the jo-trick, BTW.
Anyway, hope that helps.