This is for the Just Cause 3 XXL Edition, which has a different ID but I couldn't find it here, but hopefully it should work when activating.

XXL is only listed in-store as a <Bundle>, which doesn't send information out properly through the Steam API (and hence SG can't pull data on it to list it). [While the key form does obviously exist, it's not actually listed in the store, and (due to various oversight issues that arise when disconnecting a listing from automatic API syncing) it's SG policy to not manually list things unless the content has been removed from the store permanently and doesn't have any alternative listings which can be utilized.]

XXL has been confirmed to have the same content as XL (with some extras), so there's no issue with listing XXL under XL. ^.^ (Further, on the plus side, Just Cause XXL currently lists on Steam for $29.44, so you're actually getting a 170% CV boost by listing it under XL. :P)
(For extra assurance, RCSWE quotes a staff member on both the above points, here.)

On that note, do appreciate you clarifying that it's the complete [or would it be complete+?] edition- us DLC completionists always gotta be careful about these kind of things. ^.^ Otherwise we end up paying for the Borderlands 2 base game three times over, just to get all the DLC.. -.-;