Lol idk bout confirmation but like i said kishi is fukkin up and like you mentioned in the gaiden and the two movies he aint use it. His power up was the super sage mode not the psuedo ten tails jinjuriki form which thanks to the other bijuu lets him fly. Madara said that naruto gained the senjutsu of the sage and sasuke his eyes, when they both woke up they had they powerups activated. Then when naruto activated his bijuu cloack the other bijuus chakras fused with kuramas, thats why his skin is not glowing like the other forms but since kuruma is his main tailed beast he does retain some characteristics like the wiskers and the glowing hair and cloak. And you can see that naruto gained the sage markings on his back with each black ball representing a bijuu like the jubbi jinn. So its possible the chakra ran out after his and sasuke's last fight
Part 1 was a masterpiece
No lie Part One is one of the best Shounen Manga/Anime's of ALL TIME. I loved that shyt. I was SO hype for Part 2 and it's really a shame that a story and setup with such promise just.....was so disappointing.
I WILL say this though. I was satisfied with the ending, and seeing Naruto become the Hokage like he always dreamed was
