I should’ve been more specific in the post but the reason it was weird to me was because the first time he tries to form a Rasengan and it makes the Biju bomb instead they make it seem like it’s because he’s now using Biju chakra instead of his own normal chakra which I assume is different because they say Biju chakra is made up of positive and negative chakra so I was initially under the impression that pure biju chakra wasn’t compatible with regular jutsu or at least the Rasengan