Hmm if that were necessary, then all power states should keep the fan on for a while after running, so a device that was shut down would also keep the fans on and there would be no need to put in a requirements document that the fans must turn off to give the illusion of having shut down? To my understanding though, if no new heat is created (usually mainly by processors like CPU or GPU), keeping the fans on is not necessary in regular laptops or desktops.