So, just to see if I understand this;
The three electric motor(s), or the cockpit trim wheels physically move a reference block, whose position is measured. This position is compared to the position of the THS joint on the screw jack.
If there is a difference, the two hydraulic motors are commanded to move via electronics until the two positions are coincident.
So, the three electric motors do not move the hydraulic motor valves, they only move the trim reference block, and the hydraulic valves controlling the hydraulic motors are modulated by other means?
Have I got that right ?