It is taught that there is only one GEC, but that is not always true.I know it makes little sense to me. But that is how it was taught
A good example is when the POCO requires a ground rod connected at the meter and the metal water pipe is connected at the main panel inside (also the disconnect means and the location of the SBJ). The conductor between the ground rod and meter is a GEC. The conductor between water pipe and panel is a GEC. Two separate and distinct GEC's.