Don’t know why they would advise that. It is not how the governors work. My manuals say the fuel rack is at full fuel in the start condition. So makes no difference while cranking.
I don’t thing the “throttle” has any effect during cranking our Diesel engines. Typical injection pumps are, by design, at 100% fuel when cranking regardless of the control position. So the “throttle” setting is only effective after running.