I think you are refusing to even acknowledge that the time it takes to differentiate under control and not under control when a deadly weapon is involved could result in the officers life. They aren't robots. Given what you say here, should the officers wait until a shot has actually been fired before they draw their weapon? Be it a gun, a taser, a baton, etc?
If we cannot differentiate the line, then how can we call for the police to change their behavior?