No, that is not correct or at least it has not been. Amazon was said to intermingle the inventory in the warehouses, mixing third party products with those shipped and sold by Amazon. So that gave you zero protection.

I read that they made internal changes to tag shippings properly to reduce the risk of that behaviour, but am not sure it is true or has been effective.

I have absolutely bought multiple hard drives that were "shipped & sold by amazon" which turned out to be fake/counterfeit in some way. The serial numbers did not verify on the manufacturer's website either and they were completely DOA.