I have. I think it is YOU that ness to review. Google implemented csam scanning on their servers almost 10yrs ago right before they launched Google Photos which had unlimited storage of device pics and videos synced to their servers via your Google account. Microsoft also does server scanning.You really need to review just what other cloud services actually do vs what Apple does today.
Actually do, not proposed.
This was all in the original news post on this site that notified the world of Apple’s intention that was not mentioned in their last wwdc talking about iOS 15.
Have a good read on that original news article. Apple has postponed this far due to huge outcry and threat to disrupt sales.