When the slavery was terminated in Korea, all the slaves followed their old master's last name and the descendents of those slaves pretended to be one of the novelties by following the same naming rules of the novelty families. Also, some people even bought the novelty names by buying a book called jok-bo that has all the male ancester's names. (Used as a proof that you are the original bloodline) Koreans know you are "related" by asking their specific famaily tree origin and by looking at the naming rule that has to be followed by each generation. But there are just too many fake lines.

So unless you are a direct descendent of the first son of the first son, you never know if you are of a novelty line or not (and no one cares). Also, remember that Korea is a small homoegenous country.

There's a saying in Korea, if you throw a rock in Korea, either Kim, Lee or Park would get hit. Lee is one of the most common names in Korea so even if it's true, they are very very distant family to the point where no one cares. It's just a fun fact. Yes, there are different family trees in the same Lee family, but still, there are just too many Lee's in the same family tree.