It is much more than the direction of the air. That is merely a simplistic way of differentiating between possibilities. It is more like being right or left handed, a natural preference for jaw and tongue position with the corresponding muscle activity. Airflow is merely a product of your natural geometry. Many never find their preferences because they "ATTACK" playing instead of cuddling up with it. Our bodies talk to us. The higher levels of testosterone in many players prevents common sense listening until our inner voice starts screaming (and our playing has fallen apart).