It's annoying to switch resolution scaling settings in the properties of each game. Some games behave properly... So I wonder. When they query Windows to get the desktop resolution, does it send 720p instead of 4K because of the scaling? That would be the most logical explanation.
Honestly your symptom is rather confusing, I've never heard of it before. I know of something else that occurs with display scaling, that being when using a display scale > 100% some older games (or even new games with old APIs) end up producing a window that's far too big for the screen (because Windows doesn't know it's a game and the application is missing a manifest), but that's a rather different symptom. The resolution list doesn't change because of display scaling.
Maybe the issue you're encountering is somehow the same but causing a different problem because it's 4K at 300%, thus failing to create a window? After all at 300%, 3840x2160 is now 11520x6480, so maybe there's something to that and it's reverting to a 720p default.
Try changing the compatibility settings of the executable in case that somehow relates to your issue. Right click the executable, click properties->Compatibility, select "Change high DPI settings" , and in the drop down select "Application", then OK and Apply. You may need to use "Change settings for all users" in some edge cases".
As an additional note for any developer, the way to address this in your own program
is simply to include a manifest in the application indicating the program is display scaling aware (use Per Monitor mode). Use this even if you're using a new API, there's no harm in being sure.
