What no one has stated is how far would the plane have flown if a higher speed, probably closer to Vref L/D, had been maintained.
Vref was 135. Flaps 25 was selected at 118 kts. That's approx. 1.1 Vso instead of the typically 1.3 Vso. I've been told by a flight test engineer that Vref L/D is usually slighter higher than 1.3 Vso. If true, 1.1 Vso would reduce your gliding performance. 1.1 Vso should be worse performance anyway. Clean L/D in my current a/c is 1.35 Vsi. I wouldn't be surprised if Vso L/D is also 1.35.
I'm with S.F.L.Y. when it comes to the performance questions.
I've read the interim report. The report stated that 'the crew retracted flaps in an attempt to reduce drag'(page 4). It does not say the crews actions were successful or adviseable. It just states what the crew believed, which isn't necessarily the correct answer.
Engine power was still present. Fuel flow was 5K and 6K, or approx. 2/3's typical fuel flow. Duplicated in sim with engines at idle...crashed. The glide performance will be better with 2/3's typical fuel flow.
What the AAIB needs to do is refly the exact same scenario and do nothing. That will be the ultimate decider if the crew's actions increased, or decreased, the aircraft's performance.