Same experience here. I've already owned the base game, but none of the DLC. It let me accept Spacer's Choice, which is literally just another store entry for the base game, but you can buy the upgrade for 10$ instead of 17$.
Update: I've done some research. Apparently this version of the game is like a third-party remaster done by a different company, hence why it's a different entry in the store
My receipt, screen I selected for the game, and everything I see and can tell says it's the spacers choice edition, which is the edition that includes the DLC.
I think the giveaway just doesn't include the $9.99 dlc to upgrade the base game if you already have it to the spacers choice edition. In other words, if you have the base game only, get this giveaway and you'll have the dlc for free via spacers choice edition.
EDIT - Close to the add button Is written [Base game] and even after adding it to my library i can still see the 9$ dlc option in the menu. Either way is not too clear so I'll let the (base game) in the title.
I four different times going in it's not the worst part it's the second time they touched any of it cuz I'm like all right we got them in now we got to go further it's like body horror feelings so there's some wriggling in you and then all the sudden it's like a Delta lightning through your whole body