Oh? Why is that? Why does pain from nikyo=bad nikyo?
Again, why is applying a painful but effective nikyo lock "bad and actually useless"?
Pain is o.k. if you understand what it is and when it is o.k.
First false assumption is that pain equals good control. No, pain is bad control.
Effective equals what? Most people stop at that. Shame. There is good effective and there is bad effective.
Pain is useful in training only so that the one receiving pain can learn to 'handle' it rather than be scared of it or even moved by it. That is it's only use really. To rely on giving it in order to control is the way to a future wake up and failure. So taking the future into account that makes it useless as it prevents you getting to a good control that really works in the future.
The 'lock' in nikkyo is secondary in effectiveness to the true technique.
All the above is tempered only by the fact that along the journey of practicing control techniques they will in the early and maybe mid way along the process of refinement be quite painful but that still doesn't equal good nikkyo, only equals practicing nikkyo.
So I repeat good is painless, a joy to do and a joy to receive. Takes extra discipline.