I think this approach has a little bit more cons on this game jam because there are not that many participants, so that means people who ask their friends for help or use fake accounts will definitely get a higher position. This problem doesn't occur in the big game jams, just because there are a lot of people and rating smoothes out because of how many votes it gets.
I am not saying this is the wrong way or anything because I am not a host and I have no right to do that. But as a suggestion for the upcomming game jams, I think letting to vote only to those who are in a game jam makes more sense. Also adding a requirement like, you have to have a 10 or 15 rating to be eligible to win, would help too, because some games can get just a few ratings, and because of that, they might end up in the first place which doesn't seem right.