This is horrific if true, but what if the Nika Nika No Mi's power is the give the user the power to make what they think a reality? Luffy as a brat thought he ate a Gumu Gumu No Mi do he gained rubber properties, and through that gained the ability to be immune to lightning and thought he needed to blow air into himself to shape-shift although the name of the fruit as we know it now doesn't imply anything to do with rubber. Kaido also made implications that Snakeman showcasing the ability to bend is not a property of rubber, although Luffy may lack the knowledge on how rubber bends himself. Now that he's realized the true power of the fruit he's no longer has to blow air the achieve G4, but rather just think of doing so. His limbs are achieving much greater mass than we've ever seen before.