Also, even putting aside the fact that first-party apps necessarily have certain advantages third-party apps do not (otherwise, there’d be no distinction), apps from the same developer have broad permission to share data and resources via app groups. Gmail can talk to Google Calendar, and Google Calendar has full access to Gmail’s address book. It’s no more “fundamentally anticompetitive” for Messages and Apple Mail to have full access to your Contacts address book than it was for Meta to launch Threads by piggybacking on the existing accounts and social graph of Instagram. If it’s unfair, it’s only unfair in the way that life in general is unfair.