Indulge me for a moment I'd like to suggest the following:-
As a matter of design principle the trim wheels are intended to be able to overcome a runaway stabiliser (i.e. If the stab motor is still operating) Figure 2 of the FAA AD#2018-23-51 says "If runaway continues, hold the stabilizer trim wheel against rotation and trim the airplane manually" What this means is that the force (torque) stab motor can exert on the jackscrew must be less than that a pilot using the trim wheel is expected to be able to apply.
The troubling conclusion of this might be that:- IF stab air loads are very high and, as reported, trim wheel forces so high that it is not possible for the pilot to move the stabiliser THEN the stab motor will also not be able to move the stabiliser if column switch electric trim is applied.
I'm happy to be corrected but this would be a very bad place to be and might be relevant to understanding the final moments of ET302.