Responses
He doesn’t know, but he does suspect him. The webtoon has given Lu Feng some soft qualities in comparison to the novels. He is a man with the strongest sense of duty as an arbiter- someone the general public absolutely loathes and he fulfills his job with a cold-blooded demeanor for the most part. By this point, if he knew An Zhe was a mushroom, he would've killed him for being a xenogeneic.
I haven't read the book, but did the Arbiter on purpose leave out his diary? I think he knows that An is a mushroom and took the spore from him ... so tested him with the diary.