Why even bother typing your 2 posts if you don't even know if Xbox is dual layer or not? I don't think either of your post have any validity at all, but maybe I'm wrong...no offense meant.
Xbox discs are like multisession CDs but they are in the DVD format. The problem is that the DVD spec does not have this type of 'multisession' format. So, most PC drives and software (if not all) can not read the actual game data.