I have done this exercise, but I didn't use this format, I used the format described in Lift Off! by Ainsley Nies and Diana Larsen. It's shocking how valuable it is, I agree. It really crystallizes in everyone's mind, what we are doing, and why. I think it's easy to forget that every line of code is a decision based on conversations and knowledge of the product. So we think we can just skip that part and tell people what to do. But skipping this stuff really robs our teams of so much.