C616
Yang Fann was a person who distinguished between kindness and hatred. He was deeply grateful to Wei Changqing for helping Bai Mei break the siege at the recruitment dinner. Even though Wei Changqing might have done it unintentionally, Yang Fann still had to acknowledge his kindness.
As for why Yang Fann would want Bai Mei to thank Wei Changqing, that was a matter of distance. After all