Salute!
I would not be too quick to eliminate a simple problem with the STS or feel system that made another "simple" problem worse( if UAS is a "simple" problem), resulting in loss of control. In other words, a simple reversed wire could have reduced or even reversed back pressure. So pull back and the sucker moves faster/further than you are used to. I speak from personal experience with a reversed wire on my aileron-rudder-interconnect. The jet was very benign WRT rudder requirements unless you crammed in a gob of aileron quickly. So shortly after takeoff I did my normal "sharp" roll to course and whoa! Nose slices the opposite way big time. Scary and neutral stick and no more trouble shooting. My GIB also noticed what happened and we agreed to cautiously come bak and write it up. Sure enuf, the connectors were not polarized and a tech had inserted them the wrong way. So new item on personal checklist when doing the control movement check I would ask ground crew if rudder was moving slightly in direction of roll command.
Even the Boeing description claims that the trim/feel system increases static stability, and the tendency to get back to "trimmed" AoA/speed. So imagine that working backwards!?!
Secondly, you don't need to have a high speed stall to wind up in a high speed dive. You can get there with a slow speed stall and then an unrecoverable dive, although availabkle data does not show any real slow speeds on this plane. The 737 rudder hardovers way back then resulted in steep, high speed dives.
The data should be able to show what happened, and the CVR would be as helpful as it was in AF447.
Gums opines...