Ok, but verifying ownership of an item through smart contracts is very different from an online game in which every single step of the server-side code is hitching a ride in the blockchain... What I don't see is the advantage of the later.
The game is merely a blockchain explorer, like etherscan.io, that only consults what each wallet has and allows the game engine to unlock it for that user.
This step does not involve any added cost or latency (which would be felt only at starting up the game).
The step-by-step correlation does not happen even on a regular game with a local database. In this proposed mechanism, only the events worth being recorded (unlocking a rare collectible) would be written on the database. In this case, only the NFT items you would collect would trigger a transaction to the blockchain.