Good info from the book.
But, if those problems don't exist...
If you set RPM to a sustainable engine run speed and call it idle, any RPM drop below that point could result in an engine unable to recover.
And before you go there...
A starter does not have to spin the engine up to idle speed for ignition, thus the enriched fuel mixture.
The starter only has to spin the engine in the correct rotation requirement til ignition occurs.