Don't look into the stance too much. Like I said, that was one little microcosm of Greco-Roman to illustrate a point about imagination and conception, much like car pushing. But at the same time, the position of the feet are not integral to the stability of that configuration in the forward and back directions. You can go uneven, or go parallel, and maybe you gain some extra stability by going uneven, but traded for mobility, and on the other hand, the difference in stability is not enough to make or break stability there if you understand the basic ideas behind how to make that movement work.
And then again, the more sideways you turn, even while you gain stability/mobility from some places, the lateral movers of the body, you
lose some in those principally forward-backward movers (or up-down movers, if you want to call them that), so it is not a simple stability for mobility trade, it is in fact trading mobility in one place for mobility in another. As mentioned earlier in this thread, it is not about bracing things, it is about moving things.
This is Newton's third law of motion in action, not figuratively, literally. Everything is pushing off of something else wish slight changes in direction at each step until, a force that was going one way at one contact, ain't going there at the other. And on the other hand, it points out the body is not, apparently, one point, but a large collection of individual joints/levers which can be organized into more than one action at the same time. Biomechanical engineering for fun and profit.
There are wider principle on display there, though, that bear a striking resemblance (though not an equivalence), to things in discussion here and that I have learned elsewhere, just on different axes, writ larger, and running through different paths in this case. But yin-yang/in-yo, jin, harmonies, and other stuff. So in a sense, maybe Ueshiba did do it, in his own way, and you're looking to much into the external details of it, rather than the higher level organizing principles?