My guess is, either it was available to pre-order and then pre-ordered by people so quickly that they ran out of copies to give away. Or, it just generally the steelbook isn't available yet, and is just here as a listing for us to see until its available.
Well it never says 'exclusive' on this item, so it was never exclusive to them anyway, so they weren't pulling that stunt. And 'limited edition' doesn't have to mean every single copy, but also to the stores or websites you look at. They will have limited copies.