I still want to use random unique addresses even for important and trusted services, not just for throwaway uses. So third party domain is not an option.

I use self-hosted unique addresses mostly for registering to services, so forwarding those messages in both directions through Apple's service would expose all those services to a silent takeover via password reset by Apple's employees in control of this service. So this service is exactly as useful as those random throwaway email inboxes available on the web. More polished maybe.