That's not what Apple's plans state. The comparisons are done on phone, and are only escalated to Apple if there are more than N hash matches, at which point they are supposedly reviewed by Apple employees/contractors.

Otherwise, they'd just keep doing it on the material that's actually uploaded.

Ah, never mind, you're right:

> Apple’s method of detecting known CSAM is designed with user privacy in mind. Instead of scanning images in the cloud, the system performs on-device matching using a database of known CSAM image hashes provided by NCMEC and other child-safety organizations. Apple further transforms this database into an unreadable set of hashes, which is securely stored on users’ devices.

https://www.apple.com/child-safety/pdf/CSAM_Detection_Techni...

He is not right, though. The system used will not reveal matches to the device, only to the server and only if the threshold is reached.

> That's not what Apple's plans state. The comparisons are done on phone

Yes but as stated in the technical description, this match is against a blinded table, so the device doesn’t learn if it’s a match or not.