This was discussed on Bill Waldock's Facebook page, and winds aloft for the time in question should have produced an increase in groundspeed as the aircraft turned southwest during the climb. Waldock is a recognized expert, and often sought after as an expert witness during litigation. This doesn't make his facebook friends automatically correct, but what I recall reading seemed to be based on accurate data. A lot of those folk are people who studied with Bill as their professor at Embry-Riddle, in the crash lab at the Prescott, AZ campus (where I graduated in 1990.)
Airspeed can be extrapolated from pressure & temperature records,as well as wind vectors, and my opinion, having seen the chart, is that the accident aircraft lost airspeed and climb rate. This is consistent with an airframe icing scenario. It is quite possible that at higher angle of attack, the ice accreted somewhere it wasn't detected, or could be addressed by the available deicing gear, and that the AP in FPM climb mode could well have held the plane in a smooth climb while slowly reducing airspeed until an aggravated stall occurred. If this was sudden, and unexpected, the loading conditions and the surprise factor could have easily resulted in loss of control, or even a spin. This, of course, is educated speculation on my part, and one possible causation scenario. But regardless of the eventual determination by the board, does this discussion change anything for the readers checklist in how we fly & manage traffic under these conditions?