Water Margin: Why is Daiyu the head instructor of the Imperial Guards?

Liang Shan transmigrated and became a county magistrate in the Song Dynasty. He thought he had a historical script and was preparing to conquer the officialdom and rise to high office. However, a "ding" sounded in his mind, and the system activated: [Main Quest: Gather all 108 heroes and reshape Liangshan's destiny!] Liang Shan: ??? Even more absurdly, the list of "Constellation Generals" identified by the system seemed to look different from the original *Water Margin*, yet inexplicably matched the original's fate... Liang Shan: System, come out here and translate this for me! What the hell does "Lin Daiyu in the Snowstorm at the Mountain Temple" mean?!