Although Han Sen was unable to trace the path of the Falsified-Sky power, it was cast by a human. That meant Han Sen could tell exactly when Luo Yin cast the move.
With this knowledge, Han Sen should be able to fight in a way that would prevent his opponent from casting any Falsified-Sky powers. No matter how powerful a skill was, it was pointless if it could not be used.
But this was just a thought. He couldn't blindly go against something like that and expect things to turn out exactly as he envisioned. He knew he'd have to deliberate it more and work out exactly how he might break down those attacks.
Han Sen was not an old-fashioned man. He had doubts, so he didn't venture to the Emerald Lake as planned. Instead, he returned to a human shelter so he could go back to the Alliance.