The question is whether that "induced collapse" is a developed "Pavlovian" response to having enough done, um, with "feeling" prior. How many have shown a brand new student a nikkyo only to have them stare at you? In pain. Eyes watering. But completely oblivious to how to go down and relieve the pressure on their wrist.
In other words, an experience person manipulating your structure through the wrist such that you get the "right" feeling meaning you take the "proper" ukemi at that point. The question is whether you "really" had to go down due to the structural feel *or* if you simply feel *both* the structural manipulation ("correct" feeling) and you simultaneously realize the next feeling coming is going to be the pain. then eventually you know the structural feeling and react to that prior to actually having to move? Conditioned responses are by definition automatic and rather instantaneous and feel like they were not intentional.
I'd say that at it's best, the pain is entierly unnessesary. my experience come from training with someone that did not at all react to, or seem to feel pain in the ways other people feel it. His body would react to exhaustion but wouldnt give any pain signal, and we had to warn guests to the dojo to be carefull with his shoulders in most of the locks because there was no pain to warn him to tap out.
Nikkyo that relies on pain complianse does not work on him at all but I've still seen people that could make his feet give out under him every time so there has to be something other than pain working there. It's a lot harder to do, and I'd be very lucky to manage to do working nikkyo without causing pain one out of a hundred tries