Normally I am one of the first to assume that the words "NFT" and "blockchain" signal "scam incoming," and I still think that's the most likely explanation... but I can see a real, useful, non-criminal application for blockchain technology here, which is somewhat mind-boggling. I didn't think those existed.
The use of a blockchain for a "living world" setup provides a way to track the history of everything on a character sheet -- not only can you verify that the PC got a given item, you can see when and how they got it. And because it's decentralized, you don't rely on one company managing a server for the living world, which might vanish if the company goes out of business or just decides to pull the plug one day.
They also make an interesting point about being able to track usage. You'd be able to actually verify how many people played a given adventure or used a supplement.
Of course, the fact that there is a way it could be legit does not mean it is legit. I'm certainly not buying any.