Indeed. The centre dashboard vents supply outside fresh air, non-tempered.

And that's a great philosophy from older Mercedes. Because in the winter, driving in the middle of the night, on an isolated highway, I will have my heat blowing to my arms, legs and feet, while the cold outside air will keep me awake all the way of the trip by pointing the vents towards my face. I just reduce the amount of air coming in from the centre vent. Like wrapped in a warm blanket, perfect and the way it should be.