it's actually super easy to make a window take only half a screen in windows 8+ - move it to the edge of the screen. in windows 10, you can also move it to the corner to make it take 1/4th. shortcuts of win+left/right do similar things and also exist since win 8 at least.

now whether these people are aware of that and whether they say that having 2800x1200 window is fine for them is a completely different thing...