Earlier quoted context omitted.
NFTs are not meant for physical items, they’re digital certificates. People literally burnt a Banksy painting before auctioning its NFT.
Excuse my ignorance, because I haven't looked into NFTs too carefully, but how do you decide which blockchain (or even block) is authoritative for a given item? Seems like something like a painting could be sold on an unlimited number of chains? If it's time priority (oldest wins), what's preventing miners from copying artwork from slower chains before they're included in a block?
There seem to be ... quite a lot of them.