If the only interaction between the automated systems and the braking system is to apply more braking power and the cars breaks can significantly overpower the engine then nothing the infotainment system can do would prevent the car from coming to a complete stop.
Similarly, if the power steering was limited to applying say 5lb of force to the steering wheel (as felt by someone holding the outer edge) a driver could overpower any steering adjustments with minimal effort.
With just those two choices the risks associated with hacking the car dramatically decrease. Yes, the car could prevent someone moving, but that’s also an inherent risk from engine failure.
Referring to an event where nothing happened does not support a ‘very dangerous’ argument. If you simply mean it’s possible and after that it’s then possible that something bad would then happen then I agree.
I am simply saying it’s vastly lower risk than a car that’s impossible to steer or slow down without causing massive mechanical failure.
Infotainment systems are increasingly used as primary UI for almost anything on car that is not controlled by steering wheel and pedals and thus has to be able to communicate with almost everxthing that is in the car. Tesla is pretty extreme example of this, but it works this way for most manufacturers.