This bug made it into the release candidate. Very disappointed!
Now, to move over to the old way completely I need to switch the task identifier to the reverse DNS. But the problem is:
The SwiftUI .backgroundTask modifier can't be there at all otherwise the crash will persist
Not having the modifier means the old identifier won't be registered and thus if the old background task runs when the user updates but doesn't open the app, it will crash as the launch handler hasn't been registered
How can I migrate to the old method without causing any crashes?