Having the desktop icons and the file manager view run the same code makes perfect sense. You would want both of those things to look and behave the same.

Putting a web browser into your file manager, on the other hand, is totally unnecessary. Those are completely different things.

Gnome never did integrate a web browser into Nautilus. KDE did though, not sure if that’s still there. It was some modular thingy of course, so there’s still some separation there. I’m assuming Microsoft also did it kinda like that, they just pretended it’s totally integral in their legal defense. KDE did just because Windows did it, of course.