I have found no evidence of an area named "Bandit Freighter" in Southern Shelf. I started a new character just to be sure, and walked all over the Southern Shelf map. There were 4 and only 4 named areas: Liar's Burg, Gateway Harbor, Wreck of the Ice Sickle, and The Soaring Dragon. After discovering those areas and walking over the rest of the map, my map had no dark spots and no other areas were discovered.
Additionally, I checked my new character's WorldDiscoveryData with Gibbed. Entries there correspond to specific map dark spots. The new character's data for Southern Shelf matches that of the character I originally earned the "World Traveler" achievement for discovering all named locations in the game. This indicates that I did not miss any named locations with the new character.
It is my determination that the above map is incorrect.