No, I think you are right. Although for all directions to be south the explorers would have had to be at the north pole. If they were only near it then i suppose there would be one southerly direction.
But a compass does not point to the north pole, it points to magnetic north which is slightly off the north pole. As you get closer to the north pole this error gets greater and greater. So I'm pretty sure that a compass would be useless for navigation anyway near the north pole.
However, I haven't tried it, as I haven't been there!