> Back before Apple Silicon, running that 1440p display at “1920x1080” was actually just scaling the UI elements up

I’m almost sure that macOS can’t do that. It’s always done scaling by rendering the whole image at 2x the virtual resolution and then just displaying it on whatever screen you had. For example, for “looks like 1080p” on a 1440p screen it would draw onto a 2160p canvas (and do 2160p screenshots).