Yeah right.Actually a jinchuriki's chakra normally keeps the bijuu's in check. Naruto's training method was chakra intensive. Yamato was there incase he uses too much of his own chakra. If that happens Kurama's chakra will be free to take over. That's why Yamato was needed. At that point in the story Naruto had already made up his mind to rely on kurama. He wouldn't and didnt use kurama's chakra