What's fishy to me is the fact that they are letting this be known. Like, if you're trying to capture people who share CSAM or have it on their phone, why would you go around saying that you can now scan for it?
I think this announcement would have been well known to cause a major outrage so why say anything? I'm wondering if this is a cover up for something else. Get people talking about this in the news and getting outraged about it while something else goes unnoticed.