Meh, some of that stuff works ok. But you have exceptions to every rule. A lot of those techniques are taught as the only acceptable techniques to use in a use of force scenerio. So it is not like they are thinking that they have the real real. It just that they don't have a lot at their disposal.
If you use a technique that is not taught in DT, then you are no longer covered legally. So if you hurt something, you may have a civil suit coming towards you.