I don't have much to offer to the campfire, but thank you for the tasty s'mores! I've really enjoyed reading the different ideas on this topic! In an effort to exercise my own (newbie-ish) thinking:
The thing that comes to my mind regarding the difference between "alive" and "dead" movements/techniques, is the concept of naka ima, being in the middle of now. Through mindfulness in action we can develop a greater intuition about our bodies and how they work. Through our attention to each "individual" moment that arises, our movements can remain "alive" (or, more so, at least) and engaged to the particulars of the moment, but as soon as we start to anticipate, to skip ahead, we've essentially shut off our active/"alive" connection and overcommit to what amounts to a guess. I might get lucky and arrive in a position that still works, but it would be a happy accident, not the product of a "fully alive" connection/action.
So when I read of Nishio Sensei's comments about once something is shown it is dead I wonder if it's because the moment is gone and all that's left is the memory of form.
...My wooden nickel.
Take care, folks!