Displays Not Showing All Resolutions

Previously, to show all available resolutions, one would go to the "Displays" Pane in System Preferences, and hold down the "Option" key while selecting "Scaled". This would bring up a list of all possible resolutions for this display.

While holding down the "Option" key still causes the "Detect Displays" button to appear, it no longer allows me to see all resolutions. I have tested this on my 2014 MacBook Pro, and my wife's 2016 MacBook Pro. A search for support documents shows that there is no longer a reference to holding down the "Option" key to see all resolutions.

The last time I saw all resolutions was in March when connecting to a projector at work. Does this only work for external displays? Does anyone have any light to shine on this situation?