I can't speak for the other person, but personally I don't view it as cheating. The rules for this jam allow for games to go over the time limit - you just lose points on the "made in 3 hours" category. Cheating would be if you spent 20 hours on it and said you spent 3. Or if you claimed the assets were yours and they weren't.
Heck, mine went into overtime a bit this time too. It happens. There are some where I would have placed higher if I hit the 3 hour goal. Sometimes an idea just takes a little longer to come to fruition. Sometimes the resulting learning is worth it.