The ASIN is the product identifier, 10 characters, and it's what the buyer usually sees. Amazon would use something else behind the scenes to ensure things aren't comingled, probably FNSKU.

If the ASIN was different it wouldn't be comingled, but I don't think Amazon wants sellers all creating their own ASINs and thus new product pages when one already exists for the product.

Anybody who has used Amazon enough has witnessed when there's multiple separate listings for the same product and how annoying it is to compare.