You’d likely only be able to use it effectively once before people seek out different recording devices, or just the knowledge that cameras were disabled in that area would be as damning as any video.
Especially for any zero-day exploits. As soon as it gets used people start protecting against them so they often don’t work for very long. It would need to be a pretty big coverup to be worth burning an exploit on. Especially if it’s likely that at least one person in the area wouldn’t be susceptible and could still record it.
Looking at how bad our current system is, there’s clearly no need to prevent the videos from getting out because the officer can get away with it despite that.
And even if the officer doesn’t, the department can just scapegoat them and just keep doing the same things.
All the more reason to not waste a 0-day or risk the knowledge of a backdoor getting out.