Although there is much more content in this thread than I could even try to address, there are two topics that I can address especially well:
As someone who claims to be able to both overtone sing and express "ground strength" in all directions (to a small degree), I'd say the two are actually roughly opposites. Overtone singing is a process of analysis/reduction of complexity. You filter a complex tone to express pure tones. Whereas in internal strength, you work on a simultaneous combinination of pure expressions of ground to produce stability in all directions. One you strip down, one you build up. Anyway they do both share the idea of finding something pure and simple amidst a mess (your motor behavior being a mess before you start training).
Ok, thanks for the clarification, I have a bit of experience with Mongolian throat singing from a friend introducing me to a couple of folk rock bands, but not a lot and thought I saw some sort of similarity between the two.