From the linked editorial: > NFTs can be resold on-chain, whereas unlockable content are items that live off-chain, and therefore cannot carry on to future own

From the linked editorial: > NFTs can be resold on-chain, whereas unlockable content are items that live off-chain, and therefore cannot carry on to future owners on the blockchain. That pretty much says all you need to know about "unlockable content". Simply put, if you buy the NFT through their platform they'll give you something extra. This bonus content isn't actually part of the NFT at all and is indistinguishable from any paid digital download, apart from being bundled with the purchase of an NFT.