What makes you say this is 'common', though? Are there statistics? I've been driving an auto for ten years. If I hit either pedal in mistake for the other, I wouldn't KEEP ON pressing it in confusion. Again, why more common in automatics? The action of the right leg is EXACTLY the same as if you were driving a manual.

It may be the case that this is a mistake more common in old age, and older drivers are more likely to drive automatics, in which case the fact that the car is an auto is not a statistical cause.