I too wish iCloud backups were E2E encrypted, but that is a very different claim from "Apple assumes you desire privacy from everyone but Apple." Apple knows you want privacy from Apple; their privacy policy is quite explicit about what data Apple cannot see.
iCloud Backup is not e2e encrypted, which means Apple either gets the full iMessage and SMS history (in the case of Messages in iCloud being disabled), or gets the e2e encryption key to decrypt the synced Messages in iCloud (which they already have, due to running iCloud).
Your link describes in detail what Apple can and cannot read. They seem to want their customers to know. So how did you conclude "Apple assumes you desire privacy from everyone but Apple?"