Board Thread:Naruto Discussions/@comment-4912646-20141016191738/@comment-1512913-20141016193550

I believe Seelentau explained it like this: "there's a difference between having Tailed Beast chakra and Tailed Beast's chakra"

In other words, the Tailed Beasts inside of Naruto are basically Shadow Clones and that counts as him being their jinchuuriki. Shadow Clones despite being split chakra, can mold further chakra and spend chakra for techniques.