There is no point to struggling out of a pin if the back of your head and neck are exposed to nage.
I don't think this is a good motivator for uke to stop his action. A good pin should lock you up completely, so that struggling is no longer an option. Even thinking of wanting to struggle is locked out of your mind.
As long as I don't have the feeling of complete imobilization, I might be attempted to try to break out.
Even when it is a pin that is pretty well applied, nage better makes sure he keeps control of the situation when he is getting back on his feet or I will try to overcome him.
Because to me, there is no begin and end to a technique. There is only the continuous interaction between my partner and me.
I believe that letting my partner feel where there is an opening, is training honestly. And it should keep him aware of everting, all the time.