All you said there is based on assumptions mate, and what I understood is that you're implying that we haven't seen Naruto using RSM in spoilers because he didn't need it, right? I doubt that though, if he could deal with Toneri by himself without using RSM then we wouldn't have seen Hinata helping him which is confirmed through some spoilers.
I think UZMAKIMADARA's post above that says Kishi lowered Naruto's power to make the fight with Toneri interesting makes much more sence.
To be technical all of our posts are based on guessing and/or assumption until we get actual info saying what's what. It's safe to assume Naruto would train to learn to use full Kurama's power since when he got KM with Yang Kurama he was smashing boulders while trying to hold it, learning to use chskra arms, couldn't control his Shunshin (only used it 5 times in KM and BM together), and trying to use Rasengan but end up forming a Tbb that blew up. Naruto never completed that training because he started to get suspicious then found out the war was taking place now; Bee called the war real combat experiences which is true and all but that's no training for BM and BSM as he just used them while fighting where as KM had 12 clones fighting and Naruto received their experiences.
Not really an assumption take full Kurama's KM would be much stronger than Yin or Yang KM as it's not just double the chakra but Kurama's chakra itself it much more powerful as Choji said when Naruto and Minato have the alliance Yin and Yang Kurama chakra. So me saying full Kurama being on Yin/Yang Kurama's BM level isn't far fetch either since it makes perfect sense. Why wouldn't Naruro fight with Hinata? The theme is love and this movie is about Naruto and Hinata falling in love plus Naruto was told by Itachi to not do things on his own or else he'll become like Madara (Obito was the pic in Itachi's mind) where the power got to his ego. Kishi didn't have Naruto use his speed but 5 times in KM/BM and none in BSM to make the fights balance then Naruto used his speed on and off in RM.
No doubt Toneri powers up then Naruto does as well since some of the pic shows Toneri in his own BM like form. Plus didn't the manga said Hagoromo and Hamura sealed the Juubi in them? So Toneri might have the Bijuus/Juubi chakra that Hamura had and maybe sealed somewhere else. Who knows?