In my opinion, pain compliance techniques are using principles that, while martially valid, are tending away from the heart of aikido. I mean this not for "fuzzy-puppy" reasons. In my training, steadily less and less of pain compliance is desired or needed to effect the necessary result, and I encourage students to work to find and feel for precisely what makes the waza work without forcing pain compliance.
The physical principles that aikido strives to apply do not require pain compliance to be effective, though they certainly can and do allow this. The application of a correct
systemic torque brings the whole body into a certain reflexive manner of action, from which kuzushi flows and formal techniques then capitalize.
It isn't just twist for twist's sake -- what really works has a recognizable shape and rhythm in application that are critical. The spiral stress may be applied through the wrist, or the forearm, or the elbow, or the upper arm or the shoulder or the head and neck - or for the matter, even the legs. It can be applied more directly, with what appears to be hardly a twist at all -- (try an ankle yonkyo on a standing uke sometime .
(If you really want to work an inquisitional level torture, though -- the pinky-lock nikkyo is infamous...
Only attempt with exceeding caution and a willing and prepared uke instantly ready to slap out)