Of course it's for real. I've never ordered two entrees, but I've been with others who have. I HAVE on occasion ordered two soups, or a salad as an entree, or two desserts. On a recent cruise a couple at my table asked for and received a simple lettuce-and-tomato salad every evening, rather than the more elaborate ones that were on the menu.
By the way, the lobster tails served on cruise ships are actually crayfish tails. The crayfish look just like lobsters but do not have large claws; and they taste like lobster. As it happens, I have an allergy to real lobster, but the "lobster" tails do not trigger it.