Also, I should add that Picker used a Zone VI cold light head that had a sensor inside. The sensor connected to the timer - it actually timed the light output so that each "3-second" exposure put out the same amount of light.
Fred frequently said "Same is the same and different is different." I wondered sometimes if he was being far too picky.
I don't think it matters much what you do so long as you develop a consistent procedure, get good results, the follow that procedure. Although, if you are printing a lot of prints from a given negative, you can run into inconsistent light output. Fred said that problem is what led him to have the Zone VI head developed.