Re: Locking/pinning as pain submission...
You know, I'm not really sure. I'd say that they don't use pain compliance primarily for sure; and I suppose if I tried to resist with only one or two joints many of those techniques could eventually result in a skeletal lock situation. But, I think the best resistance is to involve as many joints as I can to distribute the power of the technique so it doesn't really feel like a skeletal lock to me. Also, I kind of have the idea (based on some experimentation) that he'd just switch what he was doing and continue messing up my balance in a new way.
As far as pinning goes, I find the yonkyo pin to be extremely difficult. The people who can pin me that way could just as easily pin me with one finger - so they don't really count. My opinion is that the yonkyo pin is never really your best bet.