A thought:
A couple of decades ago, when I was flying in a virtually identical role, in a BO105, (very similar fuel system?) of course we also had a MLA/Reserve. I have a vague recollection at that time it was 20kgs per side (I stand to be corrected)
On more than one occasion, whilst involved in important tasking, I offered the observer a choice. Either pull off the developing task and RTB, or continue with the tasking, on the understanding we would have insufficient fuel to RTB and would be landing in a field. (day or night)
On occasion we continued with the important tasking, but with a cast iron bottom line of 20kgs on either side. On reflection, it's possible I was too trusting of the accuracy of the indications available to me.
In my situation, I was able to offer that choice because we always had a duty observer back in our office with a fuel trailer and a Land Rover. We were never more than 60 minutes away from having fuel brought to us! That helped the decision making enormously.
Was such a facility available in Glasgow? Was the tasking important? Was there any pressure to extend the flight to the maximum? The operational radio conversations will undoubtedly provide some kind of insight.
I still find it incredibly difficult to believe that we are dealing here with a pilot who simply mismanaged the fuel system, and subsequent autorotation to the extent being suggested. In fact I won't believe it until I read the AAIB's final report.
Of course I accept that we are all human, and the best of us occasionally perform in ways that are difficult to understand. But I think the pilot concerned will deserve the benefit of the doubt if there is indeed any doubt at all at the end of the AAIB's investigation. I am of course aware that this tragedy has touched many lives, but on top of that, I will feel absolutely gutted for Captain Trail if the accident turns out to have been avoidable.