I don't think it's an odd reaction at all. In the wild, if you see a train and become perfectly still, sometimes they won't see you and they'll leave you alone and keep going on wuth their business.
Trains in the wild are wily creatures. I once wounded one and due to my amazing hunting skills I was able to track it for about 15 miles. I would have gotten it, too, except another one from the same herd snuck up and attacked me from behind.