Photos people send me to my Android are automatically sent through 3rd parties, either through MMS, Facebook messenger, Google Photos, or One Drive. Photos arriving on my device are almost guaranteed to be uploaded to both OneDrive and Google Photos based on how defaults of Android phones are setup.
So someone could already send hash collisions my way (purposely or inadvertently) and authoritarian governments already have access in their respective clouds (at least China does).
And yet, there are not stories of people being falsely accused of child porn due to PhotoDNA hash collisions.
Why does "on device for apple devices only" change the calculus.
You don't even have to implement the feature. All you need is really good proof that you were asked to, and now your job at Apple is secure, along with a huge raise, for years if not for life. Something commensurate with what you and they both know they would lose in the PR damage and possible EU fines.
Also, they'd probably not use a Cupertino developer. I'm sure a dev in a nation with a lot less rights is easier for this sort of work. Find a nation where the protections for employees are worse and good jobs harder to find.
Until the EU makes it a legal requirement. Which they're getting close to
Not without the risk of it being discovered (either through a leak or because someone analyzes the software on the phone), and then having a much bigger scandal on hand.