If you square around to bunt, see the ball screaming right at you, try to turn/dodge/duck/whatever, but the bat stays in the zone, it can easily be interpreted as not intentionally trying to bunt. You WERE trying to bunt initially, but you changed your action to trying to avoid being hit. As I said in a previous post and as other have mentioned, the intent is up to interpretation, but it is certainly easy to see how a bat could be in the zone, yet the batter isn't intentionally trying to bunt.