Put another way -- I think that you should be able to apply sankyo just by gripping the forearm, not the wrist or hand. Not WELL, but it should be possible to get some of the effect. Pain? Probably not. But it's probably a somewhat efficient way to forcibly rotate an arm.
That's what I was trying to imply.
When I do Sankyo this way, most people describe it as feeling it all the way up the forearm, into the elbow, the upper arm, into the shoulder, and into the side of their neck. And, I do it without twisting the wrist, at least not that much.
I know the pin you are talking about, and it's very similar to that.
There's a similar throw as well...where you hold Uke's hand like in Figure 1 and make small circles toward their center which throws them to the rear. Is that the throw you mentioned?