The Tsui Yin Manor affair was all about Kiu Fung pleading with Dr. Sit to heal Ah Chu's injury, and the wulin members gathered at the manor taking their turns trying to kill (and getting killed by) Kiu Fung. It was basically Kiu Fung vs. Chinese wulin in a free-for-all.
In the middle of all this, Deun Yin Hing's student Tam Ching showed up and was killed by Kiu Fung, and then Wan Chung Hok himself appeared and was seriously wounded by Kiu Fung as well before slinking away.
That interlude was just odd. Obviously, Tam Ching and Wan Chung Hok weren't in with the other wulin people. As an associate and a member of the Four Evils, they were every bit as much pariahs in wulin as Kiu Fung himself was at the time (even more so, perhaps, because at least Kiu Fung had previously been a hero and a respected Beggar's Union Chief). The Four Evils, at that point, had no real "beef" with Kiu Fung; their enemies were just the Deun Family of Dali.
Tam Ching and Wan Chung Hok's brief appearance didn't seem to have any point in the Tsui Yin Manor incident. The only effect was to give Kiu Fung a chance to easily manhandle Wan Chung Hok and again demonstrate how powerful his martial arts were. Aside from that, the appearance of Tam and Wan had no meaning at all.