Magic in Shadowrun is very Jungian and tied to the collective unconscious, which is why Hermeticism, i.e. learned magic, immediately tapped into those constructs when forming the basis for modern, pre-UMT magical theory. Of course, it also tended to (and still does) explain how belief shapes magic and mana such as how single or scattered individuals can create new totems/mentor spirits, as well as the phenomenon of background count and the appearances of free and summoned spirits, or how ghosts can imprint aspects of the deceased people they appear as, even if those people died a long time before the Awakening.
There's a lot of suggestion for things that cannot or will not ever be explained. This is just one more of them.
And, remember, the ties will always be there. They're not as significant as they used to be, but they're still there, and maybe it'll change or not. Who knows?