>iMessages are already E2E encrypted, but you are correct, iCloud backups are decryptable with a warrant (and that was reportedly added at the FBI's request).

Not to be nit-picky but IIRC, this isn't exactly how it went down. icloud backups have always been decryptable and Apple had announced they were planning on changing this and making them fully encrypted but when pressured by the FBI, they scraped those plans and left them the way they are.