Originally, from Nangong Chenfeng and the Eastern Ancestor's perspective, Su Han would definitely not be Wang Mo's match. They thought that as soon as the two clashed, Su Han would instantly be defeated.
Especially Nangong Chenfeng. He had already prepared himself to intervene at any moment. After all, though he felt Su Han was excessively arrogant, Su Han's potential and aptitude were beyond any doubt. This time, even though Su Han would lose to Wang Mo, it would serve to dampen Su Han's arrogance, perhaps even change his personality.
One Slash Palace would never let Su Han suffer any loss, because Su Han's talent was simply too extraordinary. Even Ji Fengyun had been defeated; once Su Han matured, he was bound to become a peerless force of nature.
Beyond potential, Su Han's commanding ability was also incredibly terrifying.