The macOS version of your app can now be included in a universal purchase, allowing customers to enjoy your app and in‑app purchases across iOS, iPadOS, macOS, watchOS, and tvOS by purchasing only once. Get started by using a single bundle ID for your apps in Xcode and setting up your app record for universal purchase in App Store Connect.
This is great in terms of giving developers more flexibility when considering branching out onto other platforms, but it could hurt their bottom lines when users come to expect this from every app.
Update: This may not be all rainbows and sunshine:
The result of this move from Apple means that developers have no choice but to abandon their existing Catalyst apps if they want to move forward to Universal Purchase, which screws over users and will make them even more upset about Catalyst. Thanks? 🤦♂️
— Steve Troughton-Smith (@stroughtonsmith) March 24, 2020