The first beastman made it pretty dangerous for the rest of the team because now the opponent won't pay any attention to surrendering before the referee has openened his mouth to declare the winner. That could potentially result in a critical wound. But then again, it's quite possible these beastmen would never surrender in the first place, not for real, that is. It might be the opponent needs to render them incapable of fighting for the match to end. So, perhaps this was actually a valuable lesson for the Lister team, what comes to beastmen.