I mean yes, but like you yourself acknowledged - that's a completely meaningless law. No intern is going to report this, because young people are just happy to have a job, no one wants to destroy their career right at the start. I myself was in that exact same position when I started - as an intern, my contract specifically said I can't be doing any productive work. Of course I did anyway. And I'm sure it still happens in every industry, because.....why wouldn't it. That's why I think unpaid internships just shouldn't be a thing at all, anywhere, unless linked to vocational schools that oversee them as a training programme.
All unpaid internships should have regular independent auditors because, as you say, interns are unlikely to report abuse of the law.
If you are an intern in a railroad you can move cars around the yard all day: you can move them to a loading dock, or to make up a larger set for a train, but at the end of the day you must move them back. However if any of those cars are moved to the dock are loaded/unloaded, or the larger train they just made leaves the yard, then they did useful work and must be paid for that.