So, the Guardian article says that it uses blockchain but is invite-only at the moment. But if it's not public, why do you need blockchain? So is it blockchain

So, the Guardian article says that it uses blockchain but is invite-only at the moment. But if it's not public, why do you need blockchain? So is it blockchain as in Bitcoin (i.e., proof of work) or "blockchain" as in hype? I hope it's not the former because proof of work wastes so much energy it's not even funny.