I think you are right. CoD isn't the only game to utilized time exclusives though. Skyrim DLC was also a timed exclusive to xbox. It just seems like Bungie/Sony are using a different method. Instead of having a short timed exclusive on the entire DLC, they are holding back small portions of content for a longer period. Not saying it is the right thing to do. It's just their strategy. I don't know if this has been done before so only time will tell if it makes a major impact on sales.