I was able to recreate your issue by using nVidia's DSR setting to play at 4K. I tried both games and you are right, A2CS screen at 4K does not stretch the screen, while AEftP does scale to the whole screen at 4K.
The reason I hadn't experienced this earlier is because I play at 1920x1080, and both games look fine at a "whole window"/"larger" game size area.