Yes, Amazon is an entirely custom, privately-coded, online P.O.S. system & database, because of this there are many exceptions that only apply with them and may not be in line with GS1's international standards. Thankfully these exceptions only apply to a very small percentage of amazon sellers (We estimate less then 1%). As a seller with amazon you will be required to know what is required of you by amazon to work within their custom ecosystem and your specific seller program.