When the Bitcoin paper originally came out, it used the word 'blockchain' to specifically mean a 'trustless distributed blockchain' where consensus is reached via mining, and that is susceptible to a 50% + 1 attack, and where the mining nodes are individual businesses that have no reason to trust each other except that the game is set up in a way that it is in their self-interest to secure the blockchain.

However, there's a use for the word 'blockchain' which is 'distributed blockchain', which is a data structure that is a chain of blocks where each includes a hash of the previous one - it's distributed amongst machines, but those fundamentally trust each other (like in case of JPMorgan chain), so there's no reason to use a 'trustless distributed blockchain'. You can't set up a miner and join Quorum and make money securing it. In such a case, quorum is probably solved just using standard distributed database algorithms like Paxos or Raft.