Naruto is an uzumaki, he has a natural affluence for chakra control. He was never bad at it, but kurama's chakra interfered with his own, which made it difficult for him to control chakra. Jiraiya had to change the seal (I don't remember how exactly) in order to teach naruto rasengan and I think summoning jutsu. He reduced the interference of kurama so that naruto could have good enough chakra control to learn said jutsu. But if you look at it, once kurama stopped interfering and started aiding, we see, like we did in the last chapter, that naruto can now create the rasengan with 1 hand, a feat that, except on extremely rare occasions and therefore exceptions to the rule, he was not able to do before. Once Kurama stopped interfering, naruto's true potential and natural skill at chakra control was able to be seen.
