It may help to check who is the actual seller, as Amazon these days is as much a distribution center for third parties as a first first party retailer.

I've heard conflicting reports on whether Amazon co-mingles its own stuff with third party sellers, but some people have certainly claimed so. What co-mingling (it's opt-in for sellers) means is that Amazon doesn't distinguish which FBA seller gave them a particular item and will ship out the one that is cheapest to ship to that particular customer. Think of it as a giant distributed pile, where every seller's Koss Porta Pro end up. Now if I order one and the warehouse closest to me has units that a different seller handed to Amazon, I might get one of those, because co-mingling means that they're treated as identical. Remember that this is opt-in on the seller's part, and it's not entirely clear to me whether (or under which circumstances) Amazon co-mingles its own stock.

Also, people can sell direct to Amazon and some of that may be counterfeit.

That means the item is faked down to the barcode.

Yes, I'm pretty sure that that's the case with the fake Koss Porta Pros (headphones). If you're going to make and sell a forgery, why would the barcode be a problem? Barcode or no, passing off the forgery as the real deal isn't exactly legal.

I don't see the point of making a fake but refraining from forging the barcode.