I have two view controllers, A and B, each under its view controller scene. When I run the app on an iPhone the segue from A to B goes from full screen to full screen as expected. When I run the app on an iPad the opening view, A, fills the entire screen but the second view, B, is presented in a square box quite smaller than the full screen size.
Use Full Screen (deprecated) is checked.
Here are the view and segue definitions: