The thought experiment that made this concrete was a sort of reductio ad absurdem:
Let's say for a moment that NFTs win worldwide support and begin to be used as proof of ownership for everything. As part of this movement, the Louvre registers an NFT signature for each item in their collection.
Now, let's say a nefarious actor manages to use social engineering and convince a naive Louvre curator to transfer the NFT ownership of the Mona Lisa.
This bad actor promptly goes to Sotheby's and asks them to list "his" Mona Lisa for sale.
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Of course, the Mona Lisa would not go anywhere. The French government would never allow it. This is an extreme example but can be walked back to less and less valuable items: would this work for an NFT of a house, a car, a computer, etc?
Unless the state decided to universally and with no exceptions enforce ownership of NFTs, they are ultimately worthless.