Is “After Dong Ping conquered Dongping Prefecture, he killed the entire family of Prefect Cheng Wanli and forcibly married his daughter.” true?

In the History of Song, there is no historical record of the military officer Dong Ping, who, because his marriage proposal was rejected by the prefect, turned against his own side when the enemy army was at the city gates, killed his colleagues, and forcibly seized a civilian woman. Such cruel and treacherous bandit behavior is actually incompatible with the so-called 'carrying out justice on behalf of Heaven' principle of the Liangshan rebels. The reason the novelist arranged such a heinous plot was largely to rigidly make up the fixed number of '108 heroes of Liangshan', thus fabricating a dark and fictional backstory for Dong Ping's joining Liangshan.