Watching this closely it appears it is not Steam nor any of the other retailers faults, it is 2k (plain and simple, full stop). Without going nuts on it, read the 'wall-o-text' post where someone explained a very viable description of the problem with a lot of hard to argue facts.
Thread:
http://steamcommunity.com/app/200510...1126936186854/
Post #259 (page 18 if showing 15 responses/page) by user Bio2hazard
Then you can look at GMGs response to the issue and see that they specifically are in touch with 2k and state there is nothing they can do beyond this as it is up to them.
Thread:
https://greenmangaming.zendesk.com/e...-12th-Nov-2013
So basically it seems the staggered release dates set by 2k, coupled with a mistake by someone to not update the proper depots as described by the person I linked above, has resulted in us all seeing an acknowledgment that we own the proper dlc, but the asset id associated with the people who did not purchase directly from Steam has yet to be updated and only 2k can do this. So...glad I both pre-ordered this and glad I did not purchase directly from Steam (although that should not have been a problem).
I hope 2k sorts this out soon because the content/expansion sounds great and I can't wait to play it.