I think this oversimplifies things. Would you “buy” the Mona Lisa from a random website with the condition that you have no rights to the property? I wouldn’t. If the Mona Lisa was put on sale by the Louvre with the aforementioned clause, I would be intrigued.

Yes.

Sometimes the point is just ownership regardless of usage. Useful as a bragging point or money laundering opportunity.

If you got to put your name on the card at the museum I'm sure it would sell for something ridiculous.

I mean, possibly, if you're the curator of the Louvre.

.. are you the curator of the Louvre?

I assume while we're on the topic that the guarantee has been written into a formal legal document, witnessed by a recognised party, that is enforceable in court, and which guarantees the terms in perpetuity?

I can give my opinion/guess to your question, and I still have no idea how it relates to NFTs.