Apple removed mentions that Hide my Email iCloud+ feature will be available for third-party apps in macOS 13 Ventura. It is not known if feature will be removed or postponed. Some of other features are marked as 'coming soon'.
Initially, it was advertised that 'Hide my Email' will be available for third-party apps simplifying process of creating new email address for a specific service.
Reference: Hide My Email Ventura feature for 3rd-party apps seemingly dropped or postponed