A SKU barcode is unique and is issued by a central authority (gs1) but you can always decide to change the title, pictures and even product category, and you ca

A SKU barcode is unique and is issued by a central authority (gs1) but you can always decide to change the title, pictures and even product category, and you can even have multiple suppliers for a single SKU. You are right that there should be a new SKU, the issue is just that it’s not in the sellers interest as they will lose all their history and reviews which effectively means that if you have a top selling product you have to start again from scratch (which if you are an established top seller in reality means you just lose all your sales and go to the bottom of the listings).