No, it is not true, just a common myth.

In the seller documentation they say they can track the source of commingled inventory - they achieve this by never putting them on the same physical shelf location.

Also mentioned by Amazon spokesman in e.g. this article: https://archive.is/ra6RT

> Amazon can also track the original seller of each unit

A fair point and important distinction, but so is the difference between "we CAN" and "we WILL/DO". That "myth" didn't come out of thin air. It's a result of of amazon not doing that unless they felt it financially prudent to do so/until enough people bitched about it.

The OP article is exhibit A for how common of an issue this was.