User blog comment:Zelron/The Elder Scrolls V: Dragonborn rumors (Imbedded deep the secrets sleep)/@comment-3186827-20121017091306/@comment-3492791-20121018013441

It's not random, it is entirely intentional. A lot of the time developers will hide little things like this in patches to cut down on the file size of the actual DLC. Some of the game files are stealthy imbedded into your game before hand to save you time later.

Or in some cases companies do it because they know very well someone will crack it and find the files. Thus they can unofficially announce new content through strategic "leaks".