I don't buy that either. Muramasa was fighting equally against Hichigo before he tempted Ichigo to use the uber attack. I mean, masked Ichigo was the mode supposed to make Ichigo equal to the asskicker Arrancars and suddenly a lone zanpakutou without a master and not even releasing itself can match that mode, forcing Ichigo to use his most powerful attack? Yeah, right. It's more reasonable to think he was using the suddenly developed, perfect reflect power also against physical attacks.