People have a misconception about Rsm. Rsm is the sage mode naruto got from hagoromo hence why it's called rikudou sage mode lol. Naruto already had the chakra of the beast so he obviously didn't get that from the sage of six paths. Before the final fight hagoromo said that the bijuu had synchronized with naruto and that he would be the place where they could reunite. This means naruto never lost the bijuus and he can still use their chakra if he needs to. So there is a difference between narutos bijuu modes and his senjustu of the six paths. Hope the idiots can understand this.