Indeed. That's what I do on my Plasma system, it's a good option.
But a new user or someone who isn't technical won't see that, they don't go digging through settings in each app, they just use the defaults.
I guess a solid compromise would be to enable this by default, and anybody who doesn't like that short descriptor can disable it.
But IMO nothing will beat the no-nonsense straightforwardness of calling OS apps immediately intuitive names. This is something I believe Gnome gets right. Go onto their GitHub and their file manager is called Nautilus, but on your system it will default to being called "Files", because they know everyone will understand what "Files" is but a lot of people would ask "Wtf is Nautilus??", same goes for other apps, e.g. "Loupe" appearing as "Image Viewer".
It literally is. It's part of the KDE Plasma desktop. It comes preinstalled.
The Vim, nano command line text editors also being there doesn't mean Kate isn't an OS app.
Would you say the Dolphin file explorer isn't an OS/system app on the basis that you can use commands like cd, mv, cp, pwd in terminal? Because I certainly wouldn't.