even a bog standard nuke temporarily exceeds solar temperatures. 0% chance all those ki blast planetary explosions don’t. It’s just authors not knowing how heat works which is insanely common. Even in something lower scale like JoJo, we had Ultimate Kars being damaged by lava when ACDC’s blood was twice as hot and didn’t burn through Joseph when some got on him lol
I don't think a lot of shonen/comic writers ever think about the fact that heat is just another form of energy, and thus the ability to tank planet shattering energy blasts should at least partially transfer to heat resistance.