[nebulous1]

I found this: https://www.forbes.com/sites/wadeshepard/2017/12/13/how-to-p...

Which says they do commingle their "sold by Amazon" stock with their FBA stock. I'm actually pretty surprised, I had no idea this was the case.

[secabeen]

Yep. They commingle because they use the UPC code as the identifying barcode for the item. If any party wants to avoid commingling, they either need to manufacture with a different barcode, or cover over the barcode with a different, vendor specific one.