The counterfeiters can create accounts faster than you can shut them down, which is likely what led them to the next step, asking Amazon to only permit certain vetted resellers.

It makes a great deal of sense if you get into the wording. Non-original doesn't necessarily mean counterfeit. It could refer to "not sold by Apple or an authorized retailer", i.e. used / refurbs.

I don't think they'd go down that path. Risk of ending up in the pile of corporations who have lost the fight against the law of first sale.

It can also refer to retail stolen and grey imports, which are a huge issue for everyone in the chain.

I'm not sure that I buy it either, but I don't think it is out of the realm of possibility that Apple would take more proactive steps than merely waiting to find counterfeits and report them, especially when a marketplace like Amazon is so poorly curated that the counterfeiters will just pop back up again.