A proof that the pok and its hash hasn't been altered since its creation.
There are lots of ways to do it. One of them would be for Fuuture to publish the hash to literally anywhere.
Public + cryptographically verifiable + distributed + append-only still does not equal blockchain, as long as we're defining blockchain as something that was not invented before 2009.
The extra governance layer that makes it a blockchain is also not trivial.