I can't answer for Larry, but when I show newbies how to very slowly apply sankyo, starting at fingertips and continuing to take out slack working up each joint, if the uke is able to relax and watch me do it to him (because there was no attack and I'm not "doing technique") then once the sankyo works all the way up the arm and through the shoulder, it will click into uke's center and structure and it will be me moving from there undermining his structure that makes him move, not pain in the arm.
Having said that....when it comes to applying sankyo quickly, in training, I'm not consistently able to do this...still working on it....