The kid obviously has talent. Perhaps its an effect of the karma seal that makes you better with chakra. Considering the fact that he can absorb jutsu without knowing ninjutsu I would say that he is more familiar with chakra than anyone realizes. But then there is his body which is similar to Delta's so you could also classify him as a cybernetic human. Perhaps these things can explain why even Jigen was shocked by how quickly he advanced. I'm thinking that his tech body along with a karma seal is too good.