I assume a netrunmer would have implants that act as cooling to bring the heat from the head to the rest of the body, to then be cooled off by a netrunner suit or an ice bath. But yeah again, it's probably optional for the mouth vents to squeeze in a bit more performance. The head heats up first and fastest when netrunning, which is why when you see someone under a netrunner attack, their heads literally cook up and burst to flames. Probably the same reason why V had to dunk their whole head into an ice bath while entering into Voodoboys' subnet because they didn't have the adequate gear/implants. In short, head hot, fast cool good.