Yes and no . . . It's established in the setting that these amulets work by exerting a slight deflecting force. They can knock aside weapons well into the range of what a man can just barely parry two-handed (say, 40 lbs.). They cannot prevent grapples, slams, or other moves that involve a whole man. In the case at hand, it was two man-sized beings getting slammed together, so the amulets couldn't do much about it. The original discoverer of this weakness was Vinz, a long time ago, when he tackled a wizard to the ground.