Actually the second version seems to make more novel assumptions. We have no (other?) proof of any cultural phenomenon older than maybe 50k years ago even existing, never mind being passed on. To imagine such a specific story surviving for such a huge amount of time while being disconnected from reality seems MUCH more unlikely than having similar stories arise independently about a hard to see but still visible star.
Also, Occam's razor says nothing about which explanation is more likely to be correct. It is simply a sensible rule about which explanation is more useful to go with when you have two that explain the same facts equally well. It's a pretty clear rule in physics when you have actual mathematical models to chose between, it's much too hand-wavy in the soft sciences like anthropology.
Could this be the result of writing being non-existent at that time? It would be hard to have knowledge passed on between generations without writing, society and preservation. If they lived a nomadic life, they probably had stories to warm up with foreigners but they could not pass a lot of information.
Also, Occam's razor says nothing about which explanation is more likely to be correct. It is simply a sensible rule about which explanation is more useful to go with when you have two that explain the same facts equally well. It's a pretty clear rule in physics when you have actual mathematical models to chose between, it's much too hand-wavy in the soft sciences like anthropology.