The full content isn't one the disc. This is actually very common now with games being made bigger. This is done usually by putting sections of map or other forms of framework preloaded onto the disc. This is done to make dlc download faster since there is less to actually be downloaded. I know a lot of people get mad about this but I really don't mind. It's better than waiting half the day for it to download on release date. I'd also suspect that some of the updates and other dlc modify and add to the framework for future dlc. With games like destiny that also keep some of the information sever side this can be even more important. Server side info would be players, enemies, gear, and most anything that isn't the map itself. That ends up being a lot that must be tracked in real time and transmitted to all the systems connected to that server. Now for this it would matter if it map data were in the disc or downloaded with the dlc, but it could not run well being streamed from the server without very long loading times. And even then it would greatly slow the servers. So functionally, pre loading some of the content onto the disc may be the best option.