From what I remember from last year, you directly choose what your overall rating for a game is (meaning when you vote on a game you choose the score for sound, music, fun, mechanics, story etc. as well as the score for the overall. So someone could (theoretically) give your game a 0 for sound, music, story, aesthetics but give your game a 5 for mechanics and fun. And if that person thinks that the only thing that matters for the overall score is fun they could rate your overall score a 5.
tldr: overall score isnt directly calculated from the other scores afaik. So just dont bother with a story if you dont want to