That's not true. Commingled inventory is stored in separate bins so that the original source of the unit can always be determined.
This is explicitly said on the Amazon seller help pages for commingling ( https://sellercentral.amazon.com/help/hub/reference/20014148... , https://sellercentral-europe.amazon.com/help/hub/reference/G... )
There is also this Financial Times article from 2019: https://archive.md/kfABj - quote from Amazon spokesman:
> The system is purposefully designed so that similar products are not placed next to or near each other, and Amazon can also track the original seller of each unit.
I guess the confusion came from the name "commingled inventory" - Amazon seems to have recognized this recently and is now referencing this feature as "virtual tracking" instead (quote from the above help pages):
> Commingling is a term that was sometimes used to refer to virtual tracking. However, virtual tracking is a more accurate term, because we trace the source of eligible products throughout the fulfillment process. Identical items from different suppliers are not stored together.