Yeah no :| ... Senjutsu is the balance of nature energy and your chakra as you've said, but if you have read the page where Naruto was being taught about senjutsu, you should known that:
How to use senjutsu for Noobs =D
Every person does have yin and yang chakra inside them, which is spiritual and physical energies which is needed to produce chakra (common knowledge). If the yin and yang energies are not balanced, you won't be able to use senjutsu perfectly, which Naruto achieved.
Now Naruto received the senjutsu of the sage, which means he gained a boost in yin and yang chakra. If he was only yang dominant, he wouldn't be able to balance the energies to achieve perfect SM. Now do you follow?
With BSM, Naruto only went into SM with his own chakra and added senjutsu to his attacks, because if he added it to you yang kurama's chakra it wouldn't have work. If it was added to Kurama's yang chakra, he shouldn't have had to add senjutsu to his attacks because the chakra would've already contained senjutsu.
Bijuudama is yin-yang release, which is also common knowledge.
Maybe it's because you have selective reading? Just a guess...
