1. Items sold by Amazon. 2. Items sold by 3rd parties and fulfilled by Amazon. 3. Items sold by 3rd parties and shipped by 3rd parties.
The problem is that items in their fulfillment centers, (1) and (2) are mixed together. Just because you buy something sold by Amazon doesn’t guarantee that you won’t be sent a counterfeit item that a 3rd party sent to amazon to use for fulfillment.
[0] https://www.forbes.com/sites/wadeshepard/2017/12/13/how-to-p...
Everything except for topical/consumable items and items with an expiration date can be conmingled.
Just a few days ago this was on the front page, an article by a small business owner selling their product on Amazon complaining both in the article and the comments that even when a product is in the brand registry they are woefully ineffective about dealing with counterfeits.
This not-Chromecast is a really bad example because it's not actually claiming to be a Chromecast, but I have certainly ordered products on Amazon and received knockoffs before. Inventory comingling makes it basically impossible to ensure you're getting what you order because even if you order from a reputable seller it might come from somebody else entirely.