If you're interested at all in polyvagal theory and somatic experiencing, the difference I think you're describing is between "freeze" response and "collapse" response. The freeze response is where "one foot is on the gas, one foot is on the breaks" - both your sympathetic (fight/flight) vagal is turned on at the SAME TIME as your dorsal vagal (shutdown). This occurs when you can no longer fight or flee. This is the deer in headlights, shocked out of movement but still very aware (perhaps hyper-aware). It feels tense, there is both extreme anxiety and extreme immobility, like a trapped feeling. I believe this is "phase one", it tends to be where people have alternating anxiety and DP, or where there's a frantic, anxiousness underneath the frozen feeling.
This is biologically different than "collapse". Collapse is when even freezing won't save you (think you're about to be attacked). Collapse is when an animal fully "plays dead", and has biologically different characteristics to freeze. In Collapse, the body is no longer tense or sending a lot of crazy signals your way - it goes limp and numb. All emotions are shut down completely in preparation for "death" (even if you aren't actually dying, your brain just perceived a threat that deeply). You may feel euphoric and completely blank out (blank mind might be a characteristics of his state). The body-brain disconnect is even stronger than it is in freeze - sensory information doesn't pass a certain level of processing. It feels like death.
I believe that you can also be somewhere between "freeze" and "collapse", it's just a matter of complex vagal nerve and electro-chemical signaling, etc.
Both are theoretically able to be moved out of, but it can be difficult.
