The reason Mr. Wu said this is because he already learned of Yang Junming's arrival in Jiang City, which surprised him despite knowing that Guan Shan wouldn't give up easily. What really surprised him was that Guan Shan could invite Yang Junming to come down from the mountain.
Yang Junming is someone who made it onto the Tuo Shi master list; even in today's Tuo Shi, no one can challenge his position.
Moreover, what's more crucial is that back then, Yang Junming was resolute in wanting to leave Tuo Shi, even rejecting Mr. Wu's personal attempts to keep him. This clearly showed that Yang Junming didn't want to be part of Tuo Shi. He wanted to return to the mundane world, yet Guan Shan managed to get him to come down personally, which left Mr. Wu both shocked and curious about what methods Guan Shan used.
With Su Changfeng's current strength, he's definitely no match for Yang Junming. If they really fought, Su Changfeng would undoubtedly die.
