What happens when someone prints a replica of a Picasso?
Nothing.
Nothing.
There are experts that can verify Picasso. Digital assets are copied verbatim with 100% fidelity and zero error.
It gets more complicated later: experts assess the credibility of the painting by examining the ownership history, if available, the signature on the painting, the quality of the work, chemical properties of the pigments and canvas, etc. They sometimes get it wrong, though (cf. Beltracchi!). It's more a probability that a work is genuine, rather than a 100% certainty.
a copy isn’t. an nft is just bytes. a copy is exactly the same as the original. it’s impossible to get an exact copy of a picasso because he himself only ever painted one. you can carbon date it etc