I also find the examples in this article a bit lacking in applicability to the subject. Not helping someone in the supermarket and being loud in the train have nothing to do with directness. However, I do believe they are Dutch traits as well (arrogance and unwillingness to serve).

We have some of the worst waiters; our (Dutch people) views of equality as being one of the most important things in society, render us unable to serve people, or to be served by others in fact. There always is some awkwardness with regards to the position of the server and the person being served. That is also why we have resolved into over automating everything in restaurants and why most waiting staff are students. Compare this to countries like France and Italy where waiting is a true profession.

In line with the 'people from Amsterdam are the most direct': I think "people from Amsterdam are the worst" is probably a more accurate statement. People who aren't from Amsterdam often state 'Amsterdam is a great city, too bad of all of those people who live there'.