Actually, this makes the most sense and maybe Kishi did it that way for a reason...That way might just be the true and pure form of getting the full power of the 10 tails... I wonder if Naruto and the Sage are the only ones that can withstand having all 9 beast chakra inside them without the gedo?
It seems clear that the chakra of all the nine bijuus are needed to meet the sage of the six paths.
But in case of obito and madara, the bijuus were sealed inside the mazo. And then the mazo was sealed inside madara/obito. Plus they aren't accepted by the bijuus either which is opposite in Naruto's case (to unlock sage's chakra form)