This is easy to replicate with the ObjectPlacement sample app. Just run the app, position the View behind you and enjoy building a tower with the blocks. Eventually the App will enter the background and exit Immersive Space.
This is actually a big problem because while you can ignore the change of scenePhase to .background this removes the chance you have to knowing the user pinched the circle X button to close the view. You can run the Hello World app, enter Immersive Space and then close the View. Immersive Space stays up and you can't get the View back. As such you need to close Immersive Space if the user closes the View (like ObjectPlacement does). Obviously if you do that and the user doesn't look at the View then it exits Immersive Space.
Either option is a bad user experience.
Being able to hide the View while in Immersive Space (such that the user can't close it) would be a good option. Unfortunately while you can hide all the content, the bar and circle X button are still visible.
A second option would be to have the View not go into the background if the user doesn't look at it iff they are in Immersive Space.
