In theory it makes it possible for other games to use the same items to make stuff in their games (I doubt this in practice)
I’ve heard this before, but there’s literally nothing preventing games from setting up some shared items on their own without NFTs. Nobody does it because companies want to keep their IP, and worrying about external items would be a nightmare to balance.
NFTs solve like 1% of the problem of sharing items. So much more goes into making them actually work. For example: NFT id 5551337 is owned by the player: now what? How do you figure out what 3d model to render? What actions can you perform? How does it integrate with other systems? All of that is going to have to be custom for every game involved on a per-item basis.