One of the first things I do when I go to train law enforcement people is ask what the rules are. I can then decide what sort of technique is appropriate for that specific agency. A lot of the people out there who think they can train police don't take that into consideration. That is something you try to point out in your books, I believe. Yes, there is no one technique that is going to work in every situation.
Every situation is unique.
There are just too many variables. The size factor alone can change everything. It used to be that police were all big men. Now, the officer can be small, tall, whatever. You have to adjust the technique.