My 2 cents.The examples such as punctuality or 'being workaholic' are all stereotypes. What is not stereotype? None. Unless there is absolutely no exceptions.
I always realize it's difficult to draw a line when to apply. However, the safe one I use to judge is always looking at how offensive the statement is. If it is offensive, let's leave it an individual issue. Most of the times, I always find out there's an exception in a negative case. That's why I never think it is fair to apply a negative attribute to the whole ethnicity like the way the topic is read.