If you root your phone and disable its ability to spy on you then that’s obviously against the desired effect. The whole point of the hash scanning is that, you, the user, cannot disable it.
Meaning there would probably be laws to force us not to tamper with that functionality.
Similar to how printer manufacturers have to look for “the yellow dots” on bank notes and refuse to print/scan.
I imagine there will be a class action suit to get it disabled on the basis that it costs me money (even if a small amount, it adds up), with no way to turn it off and it literally can do nothing good for you. In the worst case it puts you in jail for something you didn’t do and in the best case, it costs you money.
If scanning works on filesystem-level, just storing images in any non-standard format would be enough, you don't need root for that. Most likely even storing images in an sqlite would make them inaccessible for those scanners. Trying to force all apps in the world to use some scanning API for their images is unrealistic. Also you can use web apps with some website hosted in a free country with canvas drawing.
They'll just use mass-bombing by targeting most popular apps and services and that's about it. It's unrealistic to expect 100% solution, because 99% solution will be good enough.
If a competing photo storage site doesn't offer the same "feature" of scanning the files you upload, might Apple decide to prevent iOS devices from accessing it? I'm sure Apple would love to claim that the anti-trust authorities don't care about the children.
There's no precedence for any browser to censor any website outside of malicious website feature. So technically you're right, Apple surely could do that, but that will be another level of fence around garden.
