That’s an interesting rhetorical device. They are speaking as if there were more than one GCC (actually, the nature of the GCC does change over time), so there is a GCC that is not united and a GCC that is united (depending on when you make your observation). The text is referring to a GCC that is united, even if that is not the case at the present time. We could do the same with your name, using the indefinite article at first mention. Sometimes you’re sad and sometimes you’re happy — there’s a happy Soomin and a sad Soomin. “The happy Soomin is the one everyone wants to see” (definite article on subsequent mentions).