And hey to answer your questions:
Why is it on this page, and why does it appear in this specific module position????
I seems so obvious to work that way to me but i can find anything that solves my question as simple as it is.
It appears on that page because it's a component, not a module. Since it is currently a "menu-less" page all the other modules are showing up probably because you have your menu-less pages set up as "home" in your gantry settings.
Hope that explains it.
You could also set your menu-less pages in gantry to something where your rockstories and other modules aren't activated. That would solve your problem as well.
Also, you could add a menu item to your main menu for registration and link to user / main reg form and do module assignments there as well.
Cheers,
Rich