[gnopgnip]

An NFT on the blockchain can be verifired crytographically that it is the "original", it can't be duplicated, and you can transfer it to anyone if you have the private key and the gas.

A token off the blockchain controlled by a centralized group could transfer ownership without a key at all. They could issue the same one to more than one party and duplicate it. Someone else could claim to own the record and they could decide you don't anymore, they get to decide who it is sold to. Or prohibit you from transferring it at all.

[rusk]

The real world item that the token refers to is by definition “a token off the blockchain”.

[beiller]

What if two people have access to the private key? How do we prove who owns it?