The last time I saw a couples promotion come up like this in a series, the same sex "couple" was told that a couple could only be one male and one female according to the promotion's rules. We're looking at progress right here.
Had it been me and my little sister when we were still at that age, we would have no doubt gone in, posed for the picture, then took delight in cheating the system as we enjoyed our 50% off buffet.