The point about officers not saluting civilians needs amplification. As a social courtesy, an officer in uniform MAY salute a lady civilian/lady in civilian clothes if they are personally known to them. As another example, in "In Which We Serve", Captain 'E' (Noel Coward) salutes the newly married Mrs "Shorty" Blake (Kay Walsh). This is perfectly proper and correct.
The Adjutant salutes two women, neither of whom is in uniform, neither are officers, both are, in fact, civilians. A salute is reserved for Officers; you do NOT salute civilians.
Whilst the production company loads their lorry near the end, the shot is flipped, as evidenced by the letters and numbers on the index plate (number plate).