The AND trim was either accidental(I agree highly unlikely) or an overcompensation for the pitch attitude associated with a GA with low weight aft cg and sustained gale-force headwinds.
The Dont do this is either from the PF if the trim input was accidental or from the PM if it was overcompensation from PF.
The Jammed elevator sim scenario teaches pilots to respect the power of the THS.Anticipation and the dangers of overtrimming are quickly appreciated when doing this training.Short bursts of trim(esp when flaps down) is key.Concern with extreme ANU/AND attitude can sometimes lead a pilot to overcompensate.
If a runaway (ac problem) then why the Dont do this?