The "actual window manager" is not a thing. It is a relationship—between hardware, kernel, compositor, and your hand on the mouse. And like all relationships, it works best when you stop analyzing it and simply trust the deception.
This is the deepest truth:
So, after all this deconstruction, what is an actual window manager? actual window manager
That is the miracle of the actual window manager. Not that it manages windows, but that it convinces you—every single day—that windows exist at all. The "actual window manager" is not a thing