UINavigationController, Nav Bar buttons incorrect layout on iPhone Duo

When presenting a UINavigationController presented via UIViewControllerRepresentable in a sheet, the top nav bar buttons aren't correctly moving to the side bar on the front screen of the Duo. They do re-orient vertically, but they do so next to the side bar and not within it.

What am I doing wrong? This is how I am setting the buttons:

            let trimButton = UIBarButtonItem(image: UIImage(systemName: "selection.pin.in.out"), style: .plain, target: self, action: #selector(enterTrimming(_:)))

            navigationItem.leftBarButtonItem = trimButton
            navigationItem.rightBarButtonItem = cancelButton

            navigationItem.leftBarButtonItem?.isEnabled = true
            navigationItem.rightBarButtonItem?.isEnabled = true