Correct but undesirable in any aircraft
"The THS setting is not "programmed" to be left at an extreme setting - the autotrim was doing it's job perfectly and the THS setting was the natural result of the low speed, the a/c was in trim."
I think a lot of pilots are missing the poibt here. The fact that the aircraft trimmed the THS to this position without giving feedack to the pilots is a large part of the problem. Can you imagine any pilot deliberately trimming to such an extreme position especially knowing that the recovery if any significant amount of thrust was applied would be extremely difficult.
This is why when carrying out approach to stall manoevres, stalling manoebres and aerobatic manoevres pilots limit stabiliser trim settings.