These arbitrary distinctions are in your mind. The real world is messy, and there is an algorithmic fallacy at the core of your argument.

You've carefully laid out why carrying a chambered weapon is critical for minimizing the reaction time to a perceived threat. So you've explained why a suspect has his gun chambered. It's anyone's guess when that suspect decides he has "identified an immediate violent threat" in the cop near him. Now the cop, by definition, must identify and respond faster than the suspect pulling out his chambered weapon. That doesn't work well for the cop, and you've optimized away any time for his to reason and react about the situation he's in.

You haven't reasoned about anything you are saying.