Are you sure about that? I vaguely recollect reading somewhere that the 3rd party vendors stocks were indeed shared as undifferentiated stock to optimize logistics, but that Amazon kept its own stocks separate over QA reasons.
>Do you mean, if I try to avoid fakes by buying from a seller I trust, i might get inventory from the one I was trying to avoid? This makes zero sense!
For new products, that is how Amazon does it. Which will explain why many products will have inconsistent reviews about fakes. And you can ignore any review that says "Avoid seller X. He sent me a fake!" You have no way of knowing which seller's item you got.
Note that this is only for "Fulfilled by Amazon" orders. For non-FBA, the seller ships it to you directly.
And for used items, Amazon will ship you the exact one from the seller.
This is counterintuitive, appalling, and the reason I'm not going to buy any such orders again. This HN posting has enlightened me enormously. For 'customers', it's such an appalling decision, and one which if European country regulation would have been implemented would probably be deemed illegal