The facility that article talks about, OMC Alpha, is a compound in Kabul that is mostly higher up staff pukes, who as STLRN guessed, are mostly advisors.
When I was in Afghanistan in '04, my unit's main job was guarding the compound on the edge of Kabul where a lot of these folks worked, or at least came and went on business. Got to hear and see the dust cloud from an ND when one of the Army colonels (Light or Bird, can't remember) capped one into a clearing barrell from his MP5 upon entering the compound. What a pogue ass 0-5 or 0-6 needed an MP5 for I don't know, I suppose it was a matter of RHIP and the MP being a "cool gun." From what I was told by someone who was about ten feet from the colonel, when told to clear the weapon into the barrell, he totally fumbled around and was obviously clueless on how to operate the thing.
Never saw any Americans carrying AKs over there, only AMD I saw was in the hands of a European soldier from a country I can't remember.
No matter the branch though, there's always the "Hey, take my picture with this such and such" going on, just one of them things everyone does.