Certain distributors may limit where they will sell the digital distribution of FoV, but it should be available from somewhere else. The German version was the only one that had a DVD release of FoV.
The forum post may have been referring to the Xbox version (with no separate release of FoV, the only option to play the add-on is getting DKS). The only US/Canada exclusive I know of was the Xbox release pre-order bonuses.
