Woody, that's a good point. But over the years I've noticed that cars residing near our coastal regions, tend to rust up high on the body, as opposed to down low like they do in the North Eastern states.
As I mentioned before, I too noticed a small amount of "caulking like" material beneath my rubber gasket also. But it did not exhibit any adhesive properties at all, and as you pointed out, it was rather sparse in nature.