Password metadata in iCloud keychain

Has anyone looked into how metadata for stored credentials is handled in the iCloud keychain? Both LastPass and 1Password have been caught syncing metadata, e.g., URLs, unencrypted (1Password addressed the issue with the transition to their newer OPVault format).

Is all metadata synced end-to-end encrypted in the iCloud keychain or can Apple see the URLs and thereby which sites a user has stored passwords for?

Password metadata in iCloud keychain
 
 
Q