If the engine were to quit, the rotor *must* come to a level
attitude for the machine to achieve autorotation
You mean this is knowing the stuff ?
...to achieve autorotation..?????.
Give me a break.
And read with understanding.
The quote you made is referring to very low altitude situation
and climb out and slow flight, where pitch down just levels the flight
and brings you down.
By high speed rapid nose down and bringing
"the rotor .... to a level attitude"
hence stooping the airflow through it, will unload the rotor
with the known consequences.