I'm confused. If iCloud backups are not encrypted [1], and this only scans iCloud photos, why can't they just do this server side? I'm not saying server-side is

I'm confused. If iCloud backups are not encrypted [1], and this only scans iCloud photos, why can't they just do this server side? I'm not saying server-side is OK, but its at least not device side (which is obviously a slippery slope). [1] https://www.reuters.com/article/us-apple-fbi-icloud-exclusive/exclusive-apple-dropped-plan-for-encrypting-backups-after-fbi-complained-sources-idUSKBN1ZK1CT https://www.reuters.com/article/us-apple-fbi-icloud-exclusiv...