In case of Toyota, the error was not with the driver. Not having ninja reflexes when your car misinterprets throttle input as you are parking is not user error.
Reasons that a driver might not simply turn off the engine:
1. Twisting the key to turn off the engine engages the steering wheel lock, which might not be a good idea if you're moving fast.
2. Modern cars with start/stop buttons might end up with issues that disallow stopping the engine - physical button failure, or software issues related to the button handling.
3. Diesel runaway - diesels are quite difficult to stop, as they need very little external assistance, and can run on basically anything. Oil buildup in the intercooler (which any used car will have) that ends up sucked into the intake is a fairly normal way for a diesel engine to self-destruct if you're not quick enough to clutch in so you can keep the engine under control with some load.
Reasons a driver might not be able to hold the engine at full throttle:
1. Brakes seize up at load, and "full power" is certainly a lot of continuous load.
2. Brake failure.
3. The sheer difficulty of holding the car. I have once in my life stopped a diesel van that was idling in first gear using only the brake (long story), and that required a lot of effort. I would not have been able to do it if any throttle had been applied.
Reasons that a driver might not simply turn off the engine: 1. Twisting the key to turn off the engine engages the steering wheel lock, which might not be a good idea if you're moving fast. 2. Modern cars with start/stop buttons might end up with issues that disallow stopping the engine - physical button failure, or software issues related to the button handling. 3. Diesel runaway - diesels are quite difficult to stop, as they need very little external assistance, and can run on basically anything. Oil buildup in the intercooler (which any used car will have) that ends up sucked into the intake is a fairly normal way for a diesel engine to self-destruct if you're not quick enough to clutch in so you can keep the engine under control with some load.
Reasons a driver might not be able to hold the engine at full throttle: 1. Brakes seize up at load, and "full power" is certainly a lot of continuous load. 2. Brake failure. 3. The sheer difficulty of holding the car. I have once in my life stopped a diesel van that was idling in first gear using only the brake (long story), and that required a lot of effort. I would not have been able to do it if any throttle had been applied.