The only purpose I could possibly see those saw teeth serving is catching the opponents blade during the bind. I hardly think this would be worth the loss in structural integrity though, and besides makes the blade likely to snag on bone during a deep thrust or a draw cut that involves the first third of the blade. Also, Witchers don't do the bind or close draw cuts. Their whole fighting technique revolves around not getting close and cutting with the tip.
Arthur apparently had it already. That's why poor Galahad thought he was gonna get a sweet new blade.