I don't see how that makes any difference. What if someone plants bad data on your device? That would of course be a concern for cloud-scanning too.
I don't care how secure Apple says their devices are. There are companies that can crack them, and you can bet some unscrupulous people will use that against their opponents. Politicians and other influential people should be as concerned about this as everyone else. Didn't Saudis crack Bezos' phone to reveal his affair? With this tech they could make up worse stories. I believe our justice department could tell the difference between a hack and someone who actually harbors bad data most of the time, but I don't like relying on that.