Well, I think "GCC" Spec is referring to the standard options ordered by the GCC resellers, 4 door, No Nav (in dubai anyway) aso. asf.
But also, Cars that come to the GCC have different mixture in the coolants (at least my mercedes used to) also, the Fan speed is faster for GCC models. also maybe a few other components, that we do not see, are different, which for example are better in a hot climate. but most of all I think it's software related. "bing!" @120 and such. But then again I could be totally wrong, the things I listed were in my Mercedes (2006 Model) so I don't know if it's still handled this way.
edit: Also, the "Modes Menu" isn't available in the GCC... so yeah .. stuff is just missing ... lol