I just tried to buy the recently added Morrowind Collector's Pack, in the process receiving the message that I already owned some of it (since I pre-ordered the Chapter last year) but could still buy it, but when I clicked the Confirm Purchase button (I'm on the PS4 incidentally) I received the message that the transaction had failed because "You cannot own more than one unique item".
Is this intentional? If so, then I will seriously consider NOT purchasing next year's Chapter in advance.