Yes it's safety related. Turning the heater on while the airflow if off is a sure way to start a fire. It could be fixed with a relay or a solid state switch o

Yes it's safety related. Turning the heater on while the airflow if off is a sure way to start a fire. It could be fixed with a relay or a solid state switch on the heater, or with a multipolar toggle on the airspeed. But that's several cents more expensive than making it turn on at the heater switch.