My 2010 with single zone climate control. Noticed the other morning -5 degrees out. When I hit the air flow button to floor only, it sends air to floor and windshield and door window vents. Not floor only. Its going to be above freezing today will try and see if it does it again.

 

My 2010 does the same thing. Dealer said "they all do that". We even tried 2 new ones on the lot and they did it. Annoying, I know!

 

Yea, its normal.