It is quite plausible that the younger and more spry drivers react better to the acceleration and are able to successfully deploy the proper counter measures.
Another and possibly more important question is why didn't Toyota install break override systems which would signal the computer to kill the throttle? This is a common safety system found in all GM cars with electronic throttles.
"If the brake and the accelerator are in an argument, the brake wins," a spokesman at Chrysler said in describing the systems, which it began installing in 2003.