While most of the Dutch people I've heard speak did so with perfectly fluent English (and American accents -- thank you, Hollywood), you're unwittingly assuming

While most of the Dutch people I've heard speak did so with perfectly fluent English (and American accents -- thank you, Hollywood), you're unwittingly assuming he's relatively young -- my understanding is that, not surprisingly, levels of English fluency drop off somewhat rapidly with age in the current Dutch population.