And if you're coding, are you doing something routine where you only need one file open, or are you e.g. trying to learn a new library or integrating unfamiliar

And if you're coding, are you doing something routine where you only need one file open, or are you e.g. trying to learn a new library or integrating unfamiliar systems, where having documentation or APIs open is essential if you don't want to alt-tab every second line of code written? A single wide monitor works for these cases as well, or even a single small monitor if you're willing to squint a bit. But I think the assertation that "single window = focus" is a massive over-generalization that ignores a whole bunch of what some of us coders do on a day-to-day basis.