If anything posting this survey just shows little OP (and the folks over at ResetEra) understands about basic PC terminology. Primary Display Resolution is your Windows Display resolution.
There is a reason why not many people have their Windows display at 4k. I'll show it in a picture.
There. See that lovely Windows 10 (I hate it, 7 for lyfe) GUI on a 4k resolution? Can barely read the text. It's worthless. While yes, there are ways to make the display 'normalized' it's much easier to just set it to 1080p since it's so much easier on the eyes. Hope y'all console folk learned something!