Or not, cause I'm not a pilot and have never played one on TV. ;) Like I said, I'm just guessing.
He is more than right. When someone from the flight crew needs access to the flight deck, it has to be opened from the flight deck. On several occasions, I have witnessed some piece of paper or form delivered to a crew member from the ground crew and the attendant knocks on the door until it is opened from inside for the pilots to get the form. The cabin crew does not have a key to the door.
www.alpa.org/ portals/ alpa/ pressroom/ inthecockpit/ SecondaryBarriersWP_3-2013.pdf