I was at a seminar several years ago taught by Steve Parr Sensei of the BAF, where the emphasis was upon NOT relying upon pain compliance for ANY technique.
His reasoning was that following work he'd done with the police, it was obvious that somebody who was high on certain drugs wouldn't feel any pain, so it was a waste of time trying to arrest them using pain compliance. Instead they should rely upon taking centre / balance and immobilising without pain.
This makes perfect sense to me - how do you know what your attacker 'on the street' has taken, what his / her pain tolerance is, and how long you've got until the police show up?
I agree you cannot rely on pain compliance. You have to take your attacker's center. But I am thinking if you are attacked by an individual that feels no pain or feels limited pain knocking them down by taking their center isn't going to stop the attack. Pinning an attacker with or without pain seems idealistic but not probable without injury.