Yamamoto's bankai being hyperbole I just don't see. It seems that every high tier showing in bleach is claimed to be hyperbole or not as strong as its depicted. Now I know that this is coming from a physics perspective not a general power level perspective, but I'll just have to say its fiction physics. There are countless instances in manga and comics where a power in real world physics would act differently. Kizaru moving at the speed of light for instance in real world physics would cause massive damage to the planet and it's atmosphere, or some characters that are physically strong enough to move planets. In reality the planet would collapse under such a concentrated force. Not only that, but Yamamoto in fact did say that Zanka no Tachi would destroy the world if he didn't control it and/or stayed in that form for too long. And even if it were hyperbole, it is still hot enough where the Jubi would be rendered to nothing if it came in contact with him. Not its whole body but anything that touched his flames.