On the other hand, doesn't automatic gearboxes have neutral setting? Wouldn't moving into this be roughly the same as depressing the clutch on a manual gearbox?
For years, some cars have not had mechanical linkages to the automatic transmission; the shifter is just a human interface that plugs into a wire. This started in the luxury market and has wound its way down. Interfaces include joysticks resembling shifters, rotary dials, and push buttons.
The slide has been away from direct mechanical control of various car components for a while. It started with throttles, then it went to brakes (yep...) and now even some steering systems are going to steer-by-wire. Same for push-button ignition control systems. It's pretty horrifying.
Still, plenty of "runaway" cases have involved vehicles with mechanical ignition keys, mechanical transmissions, and mechanical throttles. People are just stupid, uneducated (they think that if they shift out of Drive the car will explode, ditto for shutting off the ignition...poor braking technique, like trying to "ride" the brakes to reduce speed, instead of braking HARD to STOP the car immediately) or get caught speeding and try to use it as an excuse to get out of it.