I do not agree with that statement.
All gasoline (hydrocarbon based) engines will maintain the setting throught the flight envelope we use. Our models do not exceed 1000ft +/_ in altitude , there is no reason to leave a Fat or Rich setting on the ground.
Set your engine to turn the desired RPMs on the ground while keeping in mind the MAX RPM from distributor.
Example : XX engines max is 8000RPMs , when setting it up and use whatever prop you want to achieve say 6800 on the ground. Once in the air it will loose some of the dynamic load on the prop with forward momentum and will increase RPMs,