Yea, I have noticed this before. Not this exact thing but how sometimes the manual will have features listed that aren't in the gateway. Theres even a few in the routers help that don't appear in the actual firmware.
If I had to guess, that was taken from a 802.11n draft build before those options were standarized, and once they were, it became pointless to include them as options. Maybe you have a certian hardware revision that its showing the factory flash (all dlink routers have a chip that has built in firmware and even a firmware boot order so even if you flash 3rd party you can still default). But its a neat find none the less. By the way, why do you have Extra wireless protection on? Have alot of B networks near by?
