What if Cheongsan isn't a halfbie?

Many people think Cheongsan is most likely a halfbie now because he didn't show signs of turning into a zombie and remained conscious until the bombing, but what if it's a clever red herring? Many people think Onjo could be entirely immune to the virus, but what if it's Cheongsan who's actually fully immune?

He was able to stand up to Gwinam in their fight, but Gwinam was quite weakened at that point and that could explain why he was he couldn't defeat Cheongsan, I don't think it's too likely, but I don't see it being impossible either, perhaps it was him who turned out to be immune to the virus.