I agree- The cacs have tunnels, roads etc, but it is absolutely not a rule!
I am convinced that if we went to see dug cac, there would be thousands or millions of swirls similar to other companies and completely indistinguishable.
Similarly with Heaton transparent swirls, in the past (and I think possible even now) confused with cac, Raven, etc.
But if the vortex does not have a certain structure associated with that particular company, the "ALMOST" certain identity comes only from the excavation.
So, in the absence of these requirements, we associate these swilrls with the closest possible and probable manufacturer