These concerns are spurious. You describe situations in which most cops, "nice" or not, would simply turn the camera off. Other situations include using the restroom or making personal phone calls. No one ever said the camera had to be on all the time; how would that even be enforced?

The camera should be on in any situation that might later be a subject of dispute. If it's off in such a situation, the courts should consider that a reason to disbelieve the cop who turned it off. A cop who doesn't possess the judgement to operate a camera, probably doesn't possess the judgement to carry a firearm either.