First use case: movie + website. This is possible now with picture-in-picture, but would be so much more elegant with proper top-bottom "split view." I'm just using my first awful example from above; I've resized it to a top-bottom layout. This is MacRumors YouTube channel up top and MacRumors website in Google Chrome down below.
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This example is on the 11" Pro dimensions. The standard 4:3 screen would benefit less, but it would still be great, far more useful.
I mean who doesn't want to peruse Instagram or Facebook during a boring part on that Netflix show? Or watch an iFixit youtube tutorial while reading the step-by-step webpage at the same time?
Showed the Mr this thread. He mentioned he can do this on his Note 5 in portrait mode. Like so:
Interestingly, it's not possible on Windows 10 either.