Does anybody from Ki Society background know if this was ever explicitly discussed, taught or shown by Tohei Sensei?
Never heard it discussed in the way Graham has. We talked all the time about focusing on one-point. Also many would make a clear distinction between one point and koshi. The one-point would be center. One does "settle down" (our way of discussing it -- conventional was "weight underside"). Those imply a sinking down. But the whole idea of "ground path" as espoused by others (which was the implication of Graham's post) is actually a heck of a lot more subtle and nuanced. So in essence saying "this isn't part of my vocabulary because I'm already doing it" is really just definitional sleight of hand. Unfortunately all the nuance gets lost when one waves that wand. I've been guilty of it myself.
I still want to hear more about how Western Cartesian mind/body dualism contrasts with pan-Asian concepts. It would be an interesting discussion especially considering some of Wittgenstein's ideas about how we understand our world. Pervasive and insidious forces... That made my philosophy-trained ears perk right up. Love that stuff...