First, in "The Truman Show" the protagonist was not participating with his own volition. He did not wanted to restrain himself inside. These people had a lot of contact with the outside world and still want to be left alone. The parallel is not quite valid. Second, this is natural. The island is natural, the people with their ancestry and isolationist policy are as natural as possible. Even if we'd put cameras, we'd record (just) reality, as we do in a lot of other instances among ourselves.