r.setRes does not Allow true fullscreen on Mac

While playing in editor, executing the Console Command: "r.setRes 1920x1080wf" produces the exact same results as "r.setRes 1920x1080f" which is to create a fullscreen window with a border across the top and and a 1 pixel border on both sides and bottom of the viewport.

1. On a Mac, open a third person blueprint template
2. Play in Editor
3. Press "~" to bring up the Console Command line
4. Type "r.setRes 1920x1080f" or "r.setRes 1920x1080f" to enter full screen mode
RESULT: a fullscreen window with a border across the top and and a 1 pixel border on both sides and bottom of the viewport. *See image
EXPECTED: to enter "true fullscreen" with no borders, like on Windows systems.