How to reproduce:
1. Open and build the attached project ("1133418 - UIHeirarchy Issue.zip", ensure Portrait and Portrait Upside Down in Player Settings are unchecked)
2. In the resulting Xcode project, add the attached files "SecondViewController.m" and "SecondViewController.h"
3. In the resulting Xcode project, replace "UnityAppController+ViewHandling.mm" with the attached version of this file
4. Deploy to device and observe

Expected result: Second view controller renders over Unity view (Portrait orientation should not affect it)
Actual result: Second view controller renders below Unity view

Reproducible with: 2020.3.19f1

Reproducible on:
iPhone 8 Plus (iOS 14.4.2)
iPhone 13 mini (iOS 15)

Note:
- Could not test on latest 2019.4, 2020.3 or 2021.2, 2022.1, 2022.2 versions due to differences in generated classes in Xcode ("undeclared identifiers for ‘_viewControllerForOrientation’" and other errors)