That's not how it works. Different teams work on different things. Saying "well the DLC team should have been working on the main game instead" is stupid. You don't get to decide how a company manages it's time and resources. When a game is nearly finished and all final content is finalized and ready to be bug tested, some teams begin work on DLC. This is how the industry works and there's nothing wrong with it. A few empty areas in the game files is not "locked on disc content!,,"