So is this actually a blockchain in the Bitcoin sense, or just a cryptographically-verifiable ledger, e.g. something based on a Merkle tree? They're not running

So is this actually a blockchain in the Bitcoin sense, or just a cryptographically-verifiable ledger, e.g. something based on a Merkle tree? They're not running competitive proof-of-work or anything. Or is it "blockchain" only in the buzzword sense of the term?