Watching that clip again, I noticed something interesting. This way of delivering nikyo is very similar to the way I am used to doing it. Anyway, if you look at the moment when the pin goes on, you can see that there is a moment where uke's arm briefly starts to buckle, before the rest of his body starts to move. I think that it is this "wave" of buckling that causes the pain in the wrist. Personally I try to avoid this kind of delay in application - my ideal is where uke's body is locked almost immediately, and you have a direct control over your partner's structure through the arm and shoulder skeletal system.
i consider this waza suspect.Tori raises his arms too much.His upper body is open to a counter attack.Ukes post own ure is fairly strong here. Tori uses hand power alone,Nowhere does he attempt to pin ukes wrist to his shoulder joint.I would rather bring the man in towards me , having applied sufficient pressure on the Uke , and then do the pin.Cheers, Joe,