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I found it interesting. I do notice the signals with my own dogs. I also see why a lot of dogs end up being aggressive on leashes as we as people usually approach others head on. I will be aware of that in my future dogs (lucky me neither of my German Shorthaired Pointers are leash/crate or in any way aggressive).
Love it -- haven't done it yet with my dog, but it is very methodical and well presented. I can see lots of advantages for training it.