Originally Posted by Bearfoil
THS is large, powerful, and slow moving
I don't think it is that "slow moving". I remember a figure from 1°/sec. up to 3°/sec in elecrical control, like for rudder trim, but I don't know where it is buried nor how much is the rate in manual control. Also, in this mode (back up), it could have a much higher rate than the one needed for precision trimming.
And again, I'm feeling now like the one having feed the (sleeping) Troll. You deliberatly use whatever is provided to make many assumptions based on nothing but your self ignorance. Your first assumption should be to give some credit to the engineers who designed those aircraft. You can be sure that there was a lot of thinking put in every design choice even if you don't quite understand the end result. Hence, study them in depth and, after that, come back with some constructive critisism about something you'll have really studied.