mk47at: Edit: Okay. It seems I've misread that. You cannot get DLCs in a pinata. Although I don't think that games with DLC qualify as full games…
rgnrk: You can get deluxe versions of games you already own, though. It happened to me.
That's a problem that GOG hasn't bother to fix for several years. All different editions of each game are regarded as completely separate, even if you have the base edition and the upgrade DLC it still displays the complete editions as unowned.
I'm not sure if it is laziness, incompetence or malice.
Edit: I've just noticed that you wrote the same thing a few posts later…