After leaving this thread alone until now, I have come to a tremendiously shocking conclusion.
I agree with Bruce:
There are only two self retaining pins...
Try as I might, I cannot escape my skepticism for some of the examples that have been given, provided uke is allowed to resist. From experience, I can attest that people are quite capable of getting up without the use of their arms if no one is applying direct pressure to them. (I've witnessed purple belts in bjj place both arms in their belt (no use of arms) and then proceed to not only avoid being pinned, but submit their partner).
Perhaps I missed something?