The metaphor holds though, because the receipt doesn’t say which DVD player you bought, nor is there anything stopping you from photocopying that receipt 10 times and claiming you bought eleven DVD players that day.
That’s why I specified “it’s proof as far as the person on the other end accepts it as such”, which is basically good enough to return said DVD player at the store because the store mostly trusts you. That’s as far as it goes, and it’s all NFTs might be good for.
