If a plane's autopilot steers the plane into a cliff (and such cases have happened many times, 'controlled flight into terrain' is a thing and in quite a few of those cases the autopilot was involved), we don't consider it a fault of the autopilot, it's working as intended, as it's effective job is to keep the plane straight and level, not to make smart decisions about how to fly - that's up to the pilots.

In a similar manner, if some computer system in a car holds the steering wheel straight and the speed constant, it's working just as well as a plane's autopilot even if it crashes into a parked car at full speed.