Technically, every part with the same SKU in an inventory system
should be able to be intermingled.
The problem is that the "SKU" concept is set up for selling things like drug stores selling bottles of Coca Cola, where hundreds of different franchised bottling plants will produce the same product under license, and so all have the right to slap the same SKU on the result, and it's kind of irrelevant to the consumer what licensed manufacturer produced the bottle.
While this is a common case for consumer products purchased in physical stores, it isn't at-all common for products purchased online. Apple doesn't license the manufacture of iPhones to anybody; thus, nobody but Apple should be considered a valid input for the iPhone-SKU bin in the warehouse.
Ideally, if you, as an Amazon seller, were to print the "Apple iPhone X US-version 64GB Black" UPC code on a box and send that box in to the Amazon warehouse, you should probably immediately get charged with mail fraud. Or maybe trademark infringement. (In fact, I can't see any reason why you couldn't literally trademark your own products' UPC codes, if you don't want anyone else using them.)
The problem is that the "SKU" concept is set up for selling things like drug stores selling bottles of Coca Cola, where hundreds of different franchised bottling plants will produce the same product under license, and so all have the right to slap the same SKU on the result, and it's kind of irrelevant to the consumer what licensed manufacturer produced the bottle.
While this is a common case for consumer products purchased in physical stores, it isn't at-all common for products purchased online. Apple doesn't license the manufacture of iPhones to anybody; thus, nobody but Apple should be considered a valid input for the iPhone-SKU bin in the warehouse.
Ideally, if you, as an Amazon seller, were to print the "Apple iPhone X US-version 64GB Black" UPC code on a box and send that box in to the Amazon warehouse, you should probably immediately get charged with mail fraud. Or maybe trademark infringement. (In fact, I can't see any reason why you couldn't literally trademark your own products' UPC codes, if you don't want anyone else using them.)