who simply could not get through the exam "B".
Danny; I think you have misunderstood me. In my time there were a brood of Flying Officers who had no interest in becoming Flt Lts. Thia was because they were quite happy strapping on an aeroplane a couple of times a day and propping up the bar in the evening. Flight Lieutenants could get lumbered with all sorts of extra duties which would interfere with their idyllic life. As most of them were on a 5/8/12 commission flying hours were more important than money.
Automatic promotion to Flt Lt wrecked that arrangement.