You can accomplish this with plain old cryptography. No blockchain needed.

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.

Once you're done building a working system to do the above, you'd have basically built a blockchain.

Using a very loose definition of blockchain, sure. For anything post-Satoshi, no.

The extra governance layer that makes it a blockchain is also not trivial.

So these hashes are distributed. How do we know they haven't been altered since future reveal? How does one find the "true" dataset? Trust random people on the internet?

no, since it's public, if you care so much about it, you keep a periodic snapshot of the hashes. So you're trusting yourself (and math). What's missing to be a "blockchain" in (what should be) the generally accepted definition is byzantine fault tolerance.

Right so save some time and put the hashes in a Merkel tree and publish on the Bitcoin blockchain. Now the proof can be found trustlessly and the longest PoW points to the true dataset