He didn't die but he's unconscious his heart needs to stop beating for 10 minutes minimum to be pronounce clinically dead(10 mins no oxygen to organs especially the brain = dead)
Luffy din't even stay down for 10 minutes
Luffy din't even stay down for 10 minutes
What about people who don't want to be reanimated when their heart stop beating are they pronounced clinically dead on the moment or after the doctors wait a couple minutes for their brain to leave?..
Kaido said it himself that Luffy died, there's no reason to go against the manga..