A search for 'amazon inventory commingling' brings up a bunch of articles about it; apparently it's something that you can turn on or off in your seller account

A search for 'amazon inventory commingling' brings up a bunch of articles about it; apparently it's something that you can turn on or off in your seller account. One of the articles specifically noted that if you choose to do this, and you request your items returned, you will just get that number of items from the shared inventory, which will probably include items of the same type from other sellers.