An Wenyi definitely wasn't the best in terms of technique, but his ability to assess the situation was absolutely at the top.
Lu Boyuan saw that Du Ming had stayed behind to stop Fang Rui and Su Mucheng from reaching him, so he resisted the urge to turn back and rescue Du Ming. What about An Wenyi? He was in a similar situation, being protected by Ye Xiu. He didn't hesitate and immediately had Little Cold Hands run away.
Ye Xiu was thankful.
Chen Guo didn't like this part of An Wenyi, but Ye Xiu was quite thankful for it. A healer needed this sort of calm and rationality. In the beginning, when he first met An Wenyi's Little Cold Hands, it was his clear judgement and machine-like precision that had gotten Ye Xiu's attention. Later on, he discovered that An Wenyi also possessed this rationality. For Ye Xiu, it was like buying one thing but getting another for free. How could he not be happy?