So I conclude that Apple's designers are in fact not attempting to maximize vertical space, or at least that to the extent they do care about this, they're willing to make absurd compromises in apps like Safari while not fixing the glaring issue with the overall UI.
[1] https://upload.wikimedia.org/wikipedia/en/9/98/MacOS_Montere...
Unfortunately on Windows there's this annoying slide-out animation that slows you down. It happens even if you disable UI animation.
On top of that sometimes the bar doesn't show up at all when specific windows are maximized. Which means you need to press the start button to get it out.
At some point one figures "f this shit, just toggle off auto-hide".
I do autohide in macOS on laptops tho.
Canonical had the right idea with Unity which not many people are willing to acknowledge