One should consider how much the nose has to be lengthened if the nose is a turned-up nose; or if the columella is hanging then the amount it needs to be reduced is a problem. According to the surgeon's standard they say it's safe to reduce or lengthen considering the average.
However lengthening or reducing requires high technology and skill; more than that there are cases that are not quite easy.
If we reduce the hanging columella to the length it's supposed to be then the patient thinks it's too short. It goes the same for the turned-up nose case. Therefore the nose should be reduced inbetween the average and hanging size. If the nose is reduced to the average size since the beginning then the patient would want it lengthened again since they think it got too short all of a sudden.
Lengthening a shortened nose is harder because of the paucity of autologus cartilage and other problems.
It's better to reduce the nose a bit longer than average. This picture is a case of a patient who thought the nose was long and had a reduction rhinoplasty but then thought it was too short so had it lengthened again.
The more the surgery deals with minuteness the more it gets complex.