Board Thread:Naruto Discussions/@comment-26508646-20150718215129/@comment-25442883-20150719102728

I can't say for sure, but i'd say that TSB comes from using chakra of all beasts (Naruto, Madara, Obito) not SPSM specificaly or chakra of beast+senjutsu(that's why naruto need SPSM too, but Madara and Obito had Juubi which is comprised of nature energy). It fits with what TheSooped said.