SwiftUI not displaying correctly (extend to all screen) on app across visionOS & iOS

As seen in the screenshot below, I set up a visionOS project at the beginning in Xcode 16 and later add iOS as a different platform it's also running.

And I use swiftUI as the framework for UI layout here. It runs smoothly on visionOS. However, when it comes to iOS, even if I have included modifiers as .edgesIgnoringSafeArea(.all), the display still shrinks to only weird certain area on the screen (I also tried to modify the ContentView() window size in App file and it doesn't work). Anybody has any idea for the across platform UI settings? What should I do to make the UI on iOS display normally (and it looks even more weird when it comes to Tab bars)?

Add Launch Screen.

I later found that actually I can choose Multiplatform from the template and add RealityKitContent in frameworks (if you have and need) to make it run on both iOS and visionOS. Maybe add launch screen works (idk deleted orignal file and made new one already). But the above works ... in some cases.

SwiftUI not displaying correctly (extend to all screen) on app across visionOS & iOS
 
 
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