Ten years from now we will read a leaked document stating that US authorities requested FISA Courts warrants (or similar) and made Apple scan for things other than csam. It already happened.
Court orders are easier than hacks once you iron out the legal opinions.
This technology will soon be out of Apple’s control. Higgins correctly highlights the immense pressure Apple will get from governments and other actors to bend the technology and use it for something else than csam. It will happen, people are probably already thinking how to apply such pressure. Sooner or later Apple will cave in and they will have only themselves to blame when freedom supports in Sudan or LGBTQ activists in Saudi Arabia will be jailed. The issue here is not where to draw the line, but who will draw it (spoiler: not Apple).