Board Thread:Naruto Discussions/@comment-26273905-20150403160041/@comment-945885-20150406040200

They're two different things, one is a mode, the other one is a transformation. One makes you more SO6P like, the other one makes you the TT's jinchuriki. Eh, that's questionable. The databook says that to acquire the power of the tailed beasts is the same as obtaining the power of the Sage of Six Paths, and results in the same Truthseeker Orbs (the caption also points to the Six Paths seal markings appearing on Madara's back).

There's also Madara's first bit of dialogue where he identifies Naruto as having awakened Six Paths Senjutsu and Sasuke as having awakened the Rinnegan, then declares that he has both of those powers. And, obviously, the key visual indicator that is singled out is the Six Paths seal pattern.

However, at the same time, Naruto is clearly not "transformed" when he heals Guy and kicks away Madara's Truthseeker Orb, though both of these are definitely applications of the enlightenment. Naruto says, "I feel like I can do all sorts of things now," which I think indicates that the heightened mental state isn't necessarily tied specifically into the Sage Mode transformation -- in the same way that a Sage has the knowledge of Senjutsu even when they're not actively in Sage Mode.

My thinking is that without the tailed beasts' chakra, maybe Naruto just doesn't have enough juice to fully enter Six Paths Sage Mode, as we saw it at the end of the manga. In The Last he uses Kurama Chakra Mode and Sage Mode together, and performs feats that are likely possible because of his enlightenment, like flight.