Attempting to set a new PIE window to Windowed Fullscreen mode causes both the new PIE window and the original Editor window to freeze and stop accepting input

When starting PIE in a New Editor Window on a Mac, the both the new window and original Editor window will freeze and stop responding to inputs if an attempt is made to change the window to Windowed Fullscreen mode. This can be done either by opening the console and entering the command to do so (eg. r.SetRes 1920x1080wf), or by setting the Level Blueprint to run the console command automatically after Begin Play is called or when triggered. Running the same command in a Standalone window switches the window to Windowed Fullscreen mode as expected. This behavior is not seen on Windows.

REGRESSION:
No. The same behavior was observed in 4.20.3.

1. Create a new Blank Blueprint project.
2. Start PIE in a New Editor Window.
3. Open the console.
4. Enter the following command to switch to Windowed Fullscreen mode: r.SetRes 1920x1080wf

RESULT:
Both the new PIE window and the original Editor window freeze and stop responding until the new PIE window is closed.

EXPECTED:
The new PIE window switches to Windowed Fullscreen mode in the resolution provided in the console command.