How many people select gear down flaps 15, without waiting for green landing light annunciator lights to appear or do people correctly pause before flap extension.
I ve always been guilty of no pause.
I first flew a 737 in 1977 and trained by a Boeing instructor pilot from Seattle. The technique then was "Gear down, flap 15, landing checklist to flaps"
There was no waiting for three greens then and l can't see the problem now.
Of course one can always dream up a perceived logical reason for waiting for the three greens before selecting further flap. How about this one for example. if you wait for the three greens to appear and you are interrupted by busy radio calls, you may forget to put the flaps to 15 ? I just invented that one of course; but is it logical? Of course not.