Haven’t heard about that but I think ships sailing under a Dutch flag would be treated as Dutch territory for law purposes. Harder to enforce when you’re on the high seas though. And I’m not sure percentage-wise there’s a disproportiona number of Dutch people that own seafaring ships. Most merchant ships would be owned by companies anyway and they’d probably frown upon that stuff.
Dutch merchant ships sailing through pirate infested waters might have armed guards (navy troops, mercenaries) I guess?