Crab,
I am speculating (and that is all) that the failure is an instability in the tail control system, not a stuck control, that is why the TR drive was possibly damaged enough to separate. The failure mode is a divergent oscillation of the yaw controls that leads to extremely high left pedal, then right then left at perhaps 2 Hz. Note the wiggles and left yaw just before the fun starts. Do not think of this mode as a stuck anything, it is a divergence that ends up failing the TR drive.
Regarding engine controls, all S-58's, recip and turbine, have throttles on the collective.
Regarding Blender pilot's impossibly large type comments, I find that the larger the type, the smaller the thoughts. It is wonderful to see how pilots might redesign helos to solve all the rare and almost impossible problems and not even think about the ones that get us. Should blender pilot ever actually read any accident statistics, I would hope he would use even larger type to ask for CFIT protection, or IFR capability and instruments for all helos, or fixes for all the things that actually get helos. But that would be a stretch, wouldn't it?
Asking for twist grip throttles to solve a TR problem is like donating $1,000,000 to the Cancer society not for a cure, but for fancy caskets. Sort of forgets that we might actually just fix the baseline problem, huh?