The first quote says it happens to “all photos stored […] on a user’s iPhone”. The second quote clarifies that it only happens to photos that are going to be uploaded to iCloud Photos, and that the scan is performed before the upload happens.
Man. Sometimes English is an imprecise language. I guess the second quote I posted doesn't preclude scanning all photos. It would be a weird use of wording, but if all photos were scanned all the time, then technically that sentence would still be correct.
I'm not 100% sure if this is about the on-device portion of this. Gmail and OneDrive already use this (and have for the better part of a decade) and I haven't seen any large outcry. Also, Apple has confirmed that turning off icloud photos means this doesn't work (this is separate from iCloud backups).
The difference is choice. You choose to upload your photos where you know they might be scanned. Not uploading them is a choice to keep them private. This destroys the very notion of sovereignty over your own data.
