If I recall my Rodenstock tables correctly, the Apo Rodagon N is optimised for a range to 20 x. At 20 x it bareley outperforms the Rodagon G, which is optimised from 25 x to 50 x.
Also, an f/2.8 lens is diffraction limited by f/ 5.6. At 20x, my Rodagon N is noticeable better at f/4.5 than f/5.6.
When we get up to 16x20s, it becomes important to study the focus carefully across the field. Minute irregularities become evident: the easel may be out of true, not to mention a barely out of alignment enlarger. A glass negative carrier is essential.
Older enlarging lenses ( El Nikkors, Apo Rodagons, Focotars ) may display anomalies such as a doughnut shaped area of sharpness as we exceed its range, and the only alternative is to stop down... thereby eliminating the anomoly, but at the cost of overall resolution.
As for Mr. Picker's preference for longer enlarging lenses, I always suspected it had more to do with the mechanical system of the 4x5 enlarger lacking the discretion to focus accurately a shorter enlarging lens.
An 80mm Apo Rodagon ( or any other common 80mm lens ) is optimised for lower magnification work. So there was no optical foundation in using longer lens.
Oh, well. it isn't THAT big a deal most of the time.