Yes, thats so very true.
When on Heat and directed at Face/Feet It will blow hot air out at the feet, and cold air out at the face.
If you blow hot air at the drivers face. if can make them tired.
So the best thing to do when going on a trip and it is cold, is to select face/feet. This way the cabin heats up with the air from the floor. and the driver is kept awake with fresh air at the face.
If you want hot air at the face, put the direction on face. If you want hot air at the feet, put it on feet.
Why on earth would you want hot air on feet/face anyway?
Having the selector on either face OR feet will heat the cabin up just as quick. But heating your feet up first is the best way to get warm.
Hope this answers your question.