On the Mac windows restoration in the SwiftUI app works as expected - when the app is reopened the windows from the last session are being reopened and it is up to the app to restore them to the proper state.
However on the iPad what I get is that iPadOS persists only number of windows, but not their type. So all windows will be restored as the initial/default WindowGroup even if they were not of those type while the app was running!!!
If someone has idea how to persist windows properly that would be great. But if someone has at least idea on how to disable this function (so that windows are not persisted at all) that would be certainly of great hep too. Unfortunately I can't see that it is possible to disable this on the iPad, on the Mac it should be possible, but there it works properly so no need for that...
