Imo? Stop trying to rationalize Kurapica. It was just a failure in Togashi's planning. At that point he just invented nen, and while he had the basic categories and ideas done, he didn't have very clear in his mind how skills (hatsus) would work, how powerful should be, how many skills should a hunter have, etc.
So he just gave Kurapica too many skills, and pretty good, in a too short time. It was later in the Greed Island arc where he defined the subtleties, he had a better mind to judge how many and how powerful should be the abilities of a single nen user, etc.
It never made any sense how Gon and Killua were 1 in a million kids, and Killua being a genius with previous training, needed a magnitude more of time to reach the same level.