Actually, what hes doing is another version of SIM. My son has been using dry perlite, with a cup of water in sweater boxes for a few years now. He works with small torts and it works a bit magical. Have a crazy story of one egg that appeared infertile, half full of clear liquid, until after all the clutch had hatched. He left it in the box in the incubator. A couple months later, he was putting another clutch in the incubator and that dang egg had hatched.
I have a few colubrid clutches in there now, I am not using dry perlite, more like what this poster used. So far, so good.
He may have too much ventilation. I would "think" with substrate on the dry side, you would want to limit ventilation.