In the case of those Xbox cables, my guess is that you're seeing a composite video cable there, not a coax audio cable. There are lots of third-party products out there, so I'm just guessing, but of the ones I've seen, there are two tails, each with three cables. One is the component video (blue, green, red) and the other is the standard A/V connections (red, white, yellow).
This configuration allows you to connect to an HDTV or a non-HDTV using the same cable. The expectation is that some connection(s) will go unused. For HDTVs, it's the yellow composite video connection. For SDTVs, is the component video connections.
Xbox 360 supports optical digital audio and HDMI, but not coax audio. I have used a component video switching receiver (Panasonic XR55) with this TV for several years and it's worked out very well. DirecTV HD DVR, Wii and Xbox 360 all connected with full HD and DD 5.1 support. There are also receivers that will convert HDMI signals to component that could be used with this TV. I have used switchboxes in the past as well, but find the receiver route to be an all-around better experience.