honestly, I think that description is not referring to the wire in the picture, its just referring to the audio cables that also come with the HDAV package. and as we all know, coaxial audio cables dont plug into the TV and plug into a receiver, so i guess thats why in the description of the picture he uses "obviously".
because as you can see, the audio (red/white) cable and the video cable (component RGB cables) are each on their own cable, not on one that splits 5 ways.
however the component video cable has the 1 extra wire hanging that is not plugged in. more than likely that is another video output wire.
I read that the HDAV connector that comes with the xbox360 can also so SD and connect via the normal yellow composite video cable, so that people who have the HDAV pack can play on both HD and nonHD TV's. so that would make sense if the different video outputs were on one wire.
So I really think the extra plug just hanging there is the yellow composite video cable just hanging off. either that, or its the S-Video plug just hanging off, because SVideo is also considered "Advanced" video. and on the normal XBox Advanced video packages (the S-Video one, not component) you can use it for normal composite video and S-video, whichever you choose.
So I just think the description is either.
1. wrong by talking about a cable that is not in the picture.
2. wrong by calling the yellow composite video wire the audio coaxial wire.