Although they're assuring us that they don't make mistakes. The technical term for that is either going to be "blatant deception" or "delusion". Apple are impressive but they haven't developed a tech that can't make mistakes.
Though I don't blame you at all: Read through the various hysterical posts about this and there are a lot of extraordinary misrepresentations.
I don't care. There is no way on this good earth that law enforcement is going to let them get away with that. They're claiming that they will be scanning things that are obviously child porn and ignoring it. That isn't a long term stable thing to be doing - if they think scanning for anything is ok there is no logical reason to stop here. So they probably aren't going to stop, and they certainly aren't going to announce every step they take to increase the net.
And their 1:1,000,000,000,000 number is still delusional. The system is going to produce false positives. There are more sources of error here than the cryptographic hash algorithm.