Someone is going to have to explain to me why going through all that work to set your idle in gear and check it in neutral is better than setting it in neutral and checking it in gear.
Depending on who you are, setting it in gear requires your e brake, wheel chocks, jacking the rear up, empty parking lots etc. Setting it in neutral requires applying the e brake.
Both ways require you to go through the exact same process. One way is more work and has the potential for danger. The other way has basically no potential for danger and is the same amount of work.
The FSM also tells you to put the car in neutral to set curb idle and the RPM specs they give you are for neutral as well.
What exactly is the benefit of setting it in gear?