They really arent. The movie made no sense. sasuke going against a ninjutsu user but not using preta path? lol ok. Naruto fighting a serious threat yet not using all the bijuu chakra? Lol ok.
Thanks for ignoring their feats. Sasuke might be able to absorb momo's elemental attacks, but i doubt he can absorb momo's uber bijuudama. Honestly, the bijuu chakra thing is iffy. Even if naruto didn't use all of it, he still used rikudou bsm(which should be naruto's second strongest form) against momoshiki.
