Mac OS displays exactly the same information, Windows groups windows under one icon as well. Windows shows miniatures of the windows on hover, Mac OS pops them all up to the foreground if you click the icon and lists them on right click/control click.
This theory is a subtle UX difference with larger outcomes. MacOS requires additional steps to see open windows while Windows does not.
The right click Mac OS solution is the best example. By default, right click on MacOS is deactivated. Even if someone right clicks on an app icon, that person has to click AND process the titles windows instead of seeing a visual preview as on Windows of the window.
So when you start asking questions, that terrible UI becomes a subtle UX difference.
That’s why this is all armchair designery about pet issues. You may like the way Windows works, that’s fine. But that doesn’t mean MacOS works ‘terribly’. It’s mostly just different from what you’re used to.
Nobody said that macOS has "terrible UI". Some people expressed that the window management in MacOS is inferior to Windows. I laid out UX reasons why macOS window management is inferior to Windows.
In my experience, the miniatures showed by Windows on hover are very convenient. I miss them a bit on Mac. And also the ability to quickly snap windows on sides or corners.
This theory makes little sense.