One advantage of a global menu bar is that items at the top of the screen are effectively an infinitely large target, so you can rapidly move the mouse to them without worrying about overshooting: https://en.wikipedia.org/wiki/Fitts%27s_law
But you want to select a specific menu and not just click somewhere on the whole menubar. So, it's no longer an infinitly large target and you need precision
You need a precise angle but not a precise speed. I can't speak for mice myself, but on my MacBook Pro trackpad, this is still much faster. Indeed, if I try to get the mouse cursor from somewhere near the middle of the screen to somewhere near the top, unless I go very slowly, it's essentially impossible to do it without overshooting and hitting the top. At that point I can turn around and move the cursor back down to the spot I'm trying to hit, but that requires waiting a fraction of a second, or else the high speed I accumulated from accelerating quickly will 'bounce' off the top and send me too far back down.
…Honestly, I don't know why the trackpad acceleration curve behaves that way. I've never consciously noticed this problem before right now, though, so it can't be that bad.
Anyway, of course my experience also differs in that my MacBook Pro does not have a 27" monitor. I could be using a desktop with a large monitor, but I prefer to be able to work from any chair or couch or even lying on the floor. I can see why the global menu bar would be more of a hindrance with a large monitor. But speak for yourself about what people "usually" have. :)
They didn't say infinitely large in every direction.
If you're on a Mac now, try quickly hitting the menu bar items (at the very top edge of the screen) vs the tabs (below the menu bar, not quite at the edge).
I find the difference quite significant.
Peculiarly, this convenience would flip to the opposite if the screen were touch-enabled!
