The point in clarifying that the "support of the ground" is a linear force and can be conveyed through the body without worrying very much about what sorts of stresses are in the body is that "grounding" a push, pushing with basic jin, and so on is actually fairly simple. Yet, I've been running into a number of people who are missing the fairly simple skill because they've been worrying about "dual opposing spirals". Let me deal with the topic of "dual opposing spirals" for a a bit (Jonathan... call me on any errors of logic, etc., please). After that I'll segue into a couple of other things in an attempt to cut through the mumbo-jumbo.
In the Qi paradigm, the focus is on how the body works. There is no one way for Japan and another way for China and a different way for the Ookum-Bookum Koryu. Qi is about how the body works and how strength is conveyed (thus health and other things follow and interplay).
The body tends to wind in two different ways. This is an old very basic concept about how the qi of the body works. If nothing else, just twist to the right and then twist to the left and pay attention to your legs like they're cylinders. Notice how one leg twists one way (say, "outward") and the other twists the other way ("inward") in a turn of a given direction. If you track the twisting of the whole body as a connected unit you'll notice the universality of the two directions of twist. It's so universal that it's mentioned in the Chinese classics from thousands of years ago. They draw diagrams like this:
This is the magical "dual opposing spirals", but it's really nothing more than a description of how tensions move across the body fascia in relation to way a human body moves. Notice that the lines don't 'crossover' into an "X".
If you twist pretty far and with your arms somewhat outstretched you'll notice that tension builds up torsionally as the surface of the body is stretched. You could learn to cause that same stretch without all the twisting... but that's still not what the "qi" refers to. However, the general idea is there and is fairly easy to grasp.
You can actually set up contradictory tensions all over the place, but if they're not contradictions of the "qi", you're talking about something quite different.
Regardless of any tensions you set up, right or wrong, within the body, the body will still act as a structure (once you train) that will convey the solidity of the ground through it. Hence, it's correct to just "relax" and let the structure convey the solidity of the ground. Worries about "dual opposing spirals" can come later in training because if a person doesn't have simple jin skills, the worries about other things like spirals is simply a waste of time. Learn the alphabet before trying write an essay.