Bloggs......Hang on a sec, on a normal aircraft if you thought you had an overspeed and pulled back on the stick you would most likely also trim back to assist as well.
In this case as the Pilot demanded nose up as the speed decayed it trimmed full up and stayed there most likely because the Pilots never pushed the stick forward during the stalled free fall from 38,000 feet so the Flight Control computers didn't see the need to trim forward either......
If they had applied full forward Sidestick in an attempt to un stall the wing then the stab would have moved forward to assist. It seems they not only didn't push forward they pulled back.