There is no " proof " that the content is on the disc. The only evidence of anything is that the positions on the map have already been determined ( which makes sense ), and markers were put in place to secure their position. One video shows " reef raid " as the title for the raid on the reef. I'm sure Bungie has a far more creative name for it than that, but that shows that it was a placeholder icon on the map. Makes one part of the final job easier.