My desktop is hidden by all the open apps all the time. Sure you can get there via the file manager, but it’s just another folder. And sure you can deliberately minimise all the apps. But the content is, by default hidden, and not in your face, to be stumbled upon like an inbox. Desktops can only contain closed files, and are a flaw in the UX logic.
Yes. I use that option. But as I rarely see the desktop, hiding any files or folders makes little difference to using Plasma.