Most people don't remember the rules of the road, they just adapt to common and intuition practice over years of driving.

In the USA, many or most states have laws stating that drivers must yield to pedestrians at unmarked crosswalks (every intersection is a legal crosswalk), but most drivers don't know that "unmarked crosswalks" exist.

I think the Dutch people posting here know whether or not they reach across their body and open their driver-side door with their right hand. So I believe them when they say the article is wrong.