That is possible, given the protective disc around the spring. But it is also possible that your 14500 is too long to allow the tail cap to screw down fully. That can happen with some protected cells.My s15 just arrived today. Overall, I really like the light with one major exception. My Keeppower 14500's will not work in this light. It appears the button on the battery is not quite long enough. This is a shame since I have more coming for this particular light!
EDIT: It seems like the issue is the top - the plastic disc in the head does serve as reverse-polarity protection.