> If you've worked in computer security long enough, you know that Apple could already have added a backdoor into every build of iOS that allows the government to read any material on your device they chose to read.

Yes. They could. However, getting caught doing that, from Apple, would be an absolute disaster for them, and they've both made the right statements and made the right actions in terms of things like physical device security (moving more and more into the secure enclave to protect against demonstrated attacks).

It's entirely possible they've done this for specific cases, with a gag order, and nobody knows. However, it cannot be widespread, or it would end up known.

This, however, is adding a blackbox image matching algorithm (we know it's not matching image file data based on statements about how it's robust against cropping/rotation/resizing/etc), and a blackbox database of "Stuff claimed to be Really Bad." There is no way to audit the database and see what's in it, because of the one way nature of hash functions, and there's almost certainly not a pile of the source material laying around for audit reasons (because that would be a really nasty legal problem). So you've got a "Trust us, this stuff is bad" database, and a "Trust us, it matches images accurately" hash function.

And, if those find enough matches (also unspecified), you get yourself reported directly to the various authorities.

It's guilt by algorithm, across every single Apple device (running the latest OS, etc... handwave as needed).

That's very, very different from a customized backdoor deployed to a small number of phones.