Is Fullscreen Mode Dirty always returns true for Windowed Fullscreen

Is FullscreenMode Dirty is meant to track if the Fullscreen mode has changed from what it is currently set to. This does not function correctly for Windowed Fullscreen and always prints true even if the setting is currently Windowed Fullscreen.

Regression?: No
This occurred as far back as 4.13

1. Download the attached project
2. Run the game in Standalone mode
3. Press T to change the Fullscreen mode to Fullscreen and press A to apply it, note that it is printing "False" for "Is FullscreenMode Dirty"
4. Press Y to change the Fullscreen mode to Windowed and press A to apply it, note that it is printing "False" for "Is FullscreenMode Dirty"
5. Press U to change the Fullscreen mode to Windowed Fullscreen and press A to apply it
   Result: "True" is being printed from "Is FullscreenMode Dirty"
   Expected: "False" is printed from "Is FullscreenMode Dirty"