Dude is worse off not only by doing the physical work by fanning, but he's also standing, which means his head is much higher than the sitting girls' heads. Hot air goes up. I actually recently saw in a Youtube short a private Japanese sauna that was build entirely wrong with the benches not being raised at all. Unless there was some sort of powered air mixing going on in the sauna, it would be miserable. Maybe there are more flawed saunas in Japan like that, thus also giving the various mangaka the wrong idea about how it works.