This is just a little thought I've been playing with. I'm not sure if I'm ready to commit to this theory, but hey, that's what a theory is, right?
I looked it up just to be sure. A theory is "a supposition or a system of ideas intended to explain something, especially one based on general principles independent of the thing to be explained."
So, this "Coffee Mug Theory of Writing Process" is a theory because it's intended to explain something.
Whether it does explain anything remains to be seen.