If there is no third connection, like via the casing of the ventilator, you can't get two functions by just two wires (leaving aside specially modulated voltage).

If the ventilator runs on AC it would not matter how you pair the couplings. In case of DC it could run backwards, which may not be eaysy to recognize and might not even matter.

Furthermore, what is the difference in meaning at a ventilator between rotation and airflow?