> NFT people do not claim that non-fungible means "you cannot mint two tokens representing the same thing".
What NFT people do is argue that the uniqueness of individual tokens matters. It doesn't. They try to have their cake and eat it too, they try to argue that the NFT's link to the individual artwork doesn't matter when evaluating the technology, but that it does matter when trying to determine whether or not NFTs have value.
There are two ideas being conflated here about fungibility. If you want to argue that NFTs actually represent an artwork in some way, and that owning an NFT is somewhat similar to owning a piece of art or that it carries some meaningful connection to that artwork, then for all practical purposes NFTs are fungible resources. The attributes of an NFT that link it to an artwork are not guaranteed to be unique.
If you want to argue that the part of an NFT that matters is the individual token itself, then sure, they're non-fungible. But if that's all we care about then they're also worthless, because nobody cares about owning serial numbers, they care about owning a token that meaningfully points towards a socially or personally valuable item. They care about the thing that the token represents.
The only reason why one NFT is worth more than another is because of who issued it and what it's linked to. So to argue that the individual token's uniqueness is the only thing that matters is to reject the entire relationship between NFTs and artwork.
I brought this up elsewhere, but if I pull a $20 bill out of my pocket, it will have a unique serial number on it that corresponds to only that bill, and no other bill. So technically, by your criteria, a $20 bill is just as non-fungible as an NFT. It's technically unique in the same way that an NFT is.
But what I'm getting at with that comparison is that it's not enough to have each NFT be technically unique. They have to be unique in a way that matters, they have to be unique in a way that somebody would care about. Otherwise you might as well just collect $20 bills. Back to my original point, if the only thing that NFTs are providing is that the token itself is unique, that's not an improvement over any of our existing systems. You can already issue unique tokens without bringing NFTs into the equation, issuing a unique token is easy.