If it is like the PF really did not move the #2 lever, then to me it looks more like a transition problem from one design philosophy to another. I really think it is difficult to change "deep" habits and expectations in a few days of training. Maybe that point was taken too lightheartedly until now and it seems that it was the pilot flying who was new to this.
But another question I did not read in the entire thread: How come everybody is sure that the lever sensor wasn't broken? What if they operated the bird by the book but the electronic never sensed that #2 was drawn to idle power? The DFDR cannot show the position of the thrust levers themselves, only the data produced by the levers' sensors. At least to me it looks to be VERY important where the TL physically was in the wrecked cockpit.