From what I understand, the main goal is to fix the problem that non-native (1:1 pixel mapping) resolutions and scaling look worse than native. This is a problem when you ship high-dpi displays that need UI scaling in order for things to be readable. Apple's solution was to render everything at a higher, non-native resolution so that images were always downscaled to fit the display.
So to oversimplify, Windows can have a problem where if you are running 1.5X scaling so text is big enough, you can't fit 4K of native pixels on a 4K display so videos are blurry. If instead you were rendering a scaled image to a 6K framebuffer and then downscaling to 4K, there would be minimal loss of resolution.
So to oversimplify, Windows can have a problem where if you are running 1.5X scaling so text is big enough, you can't fit 4K of native pixels on a 4K display so videos are blurry. If instead you were rendering a scaled image to a 6K framebuffer and then downscaling to 4K, there would be minimal loss of resolution.