It's still an entirely implausible scenario. There's too many hypotheticals here to even properly argue this as "cross-game metaverse trading" is kind of hand wavey in how it would be implemented at all, but getting back to the core issue of centralization just being a mask for trust and authority. If there's truly no trust between the parties, which would be extremely odd of them to set up a giant cross-game metaverse in the first place, it would be better to have an agreed upon third party trustee host the data. Or each host their respective data with an API for others to access it when needed. And ultimately, the final authority lies with each game itself on how it implements that data. They can read whatever data they like off the blockchain, but how it's implemented locally is their final say, the game can warp that data or ignore it in any way it wishes. To say nothing of what that data looks like. Does the blockchain contain the entirety of the model, texture, and stats for all games implementing that item? Does that lock the schema in place at inception? How do new games enter the metaverse then? What about bugs? What about balancing of stats and economy across multiple games, it's hard enough in one. Are all the games similar in nature? How do you implement an AK-47 from a CoD-like game into a fantasy MMO?

The whole premise is nonsense.