I don't see how that could affect the signal from the ECU to the throttle motor on the 8F.
The ECU uses the tachometer signal to sense RPM and then governs the operation of the throttle motor to limit the RPM.
If the trucks have SAS on them, there are some other parameters fed into the ECU such as vehicle speed, mast height, mast tilt angle and steer axle yaw from sensors. The RPM is reduced on SAS models according to input to the ECU from sensors about the conditions the truck is operating under at any given time.
I fail to see how the action you describe could make such a complex watchdog system go haywire, but if this does turn out to be possible.........Toyota has a huge liability problem being dumped into their lap.
Have you actually seen some damage that could be attributed to excessive RPM/vehicle speed or is it just anecdotal rumour that makes you ask?