This was going to be my guess, as that's what other cruise lines do β the land tour is long enough going from Flam to Gudvangen, looping back to Flam would be longer and no more scenic. Everyone will experience the sail-in up the fjord to Flam; those who don't do a full-day excursion will also experience sailing back and up the side fjord to Gudvangen; then everyone will experience sailing out of the Gudvangen fjord and to the sea. No matter which choice you make, it's a great day! [I recommend the Flam Railway/Gudvangen excursion.]