Interesting. You said you train police officers correct? If I may, let's assume GZ's account is accurate as can be given the circumstances. In order to insert a police officer into the hypothetical, we'd change a few particulars.
Please don't answer this if I'm mistaken in the assumptions. Correct me and then provide your answer if you would be so kind.
Officer has notified dispatch she/he needs to investigate a pedestrian. The pedestrian approaches the car stares at plains clothes police officer, then leaves the immediate vicinity. The officer exits his/her vehicle not intending to follow/pursue the pedestrian but to determine if he/she can locate where the pedestrian was heading. To this point, again assuming GZ's account is accurate, would you advise a citizen to act differently?
It's easy to say in hindsight, don't get out of your vehicle. When I imagine, again assuming it's accurate, what would I have done? I'd have gotten out. I'm not going to let the pedestrian move away and not be able to inform the arriving law enforcement anything more than he left here heading that way. It's MY neighborhood, I live here.
As to when the altercation initiated, I believe you've offered there would be no difference.
I cringe when you say there would be no charges filed unless the officer was white. That's a horrible representation of the burden law enforcement operates, but an accurate representation of the sad state of our society.