Earlier quoted context omitted.
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.
Has this co-mingling of sold by Amazon ever actually been documented at any scale beyond “extremely rare stock/pick” mistake? I am of course aware of the option for manufacturers to enable this for their registered products on FBA - and it may not have been optional at one point in time. When I researched this a while ago I was unable to come up with much compelling evidence that it was an actual thing. It certainly…
F-4 Storage
We will provide storage services as described in these FBA Service Terms once we confirm receipt of delivery. We will keep electronic records that track inventory of Units by identifying the number of Units stored in any fulfillment center. We will not be required to physically mark or segregate Units from other inventory units (e.g., products with the same Amazon standard identification number) owned by us, our Affiliates or third parties in the applicable fulfillment center(s).
https://sellercentral.amazon.com/help/hub/reference/external...
That combined with years and years of anecdotal reports of this happening certainly suggests a "where there's smoke there's fire" situation to me.