Nothing clever like that - merely my deduction. Four conditions for PWS to be on:
1. a/c below 2300 ft agl
2. PWS switch in AUTO
3. Either engine is running.
Now this might be the case on an engine run by a ground engineer - which would mean that the radar is transmitting even though the switch is OFF. This is undesirable.
So another condition - ATC on - is included. This implies there are pilots in the cockpit taxying out for take-off. Make sense?