Naruto stated he was holding back and the manga confirms it even more with sasuke getting reckt by kaguya with a single chakra palm meanwhile naruto was matching several punching of kaguyas chakra palms (and thats without boil release).They're talking about their personalities not their powers. Naruto and Sasuke have Indra and Ashura's genes, Sasuke will always have the stronger chakra which is why Naruto needs bijuu and Sage Mode to match his avatar.
Sasuke isn't using bijuu and NE to match RSM Naruto's avatar
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If naruto where serious in that he would had stomped sasuke easily.