heating and engine temp

You know how on water cooled cars if the engine is overheating you can turn the heater on full blast and cool the engine a bit as you are creating more airflow over the coolant via the heater coil. Well is the same true for aircooled engines? If you open up the heating vents does it improve the airflow through the engine or does it make it less efficient?

I know vw heaters are not great at the best of times but I seem to have noticed some weirdness with the oil temp when I open up the vents. Maybe just coincidence.