I have seen people call Hivemind a "layer 2", and non-chalantly calling to move more of the blockchain to layer 2.
For "real" layer 2, there needs to be fraud proofs or validation proofs that verifies everything on layer 2 with the same security and consensus mechanisms of layer 1. You have to tread very carefully moving stuff outside the blockchain. Otherwise, these are just hybrid centralized solutions.
See: optimistic rollups and plasma (fraud proofs) or zk Rollups (validation proofs) on ethereum for how it works.
Where are the fraud proofs or validation proofs for Hivemind? If I'm not mistaken, it's just a centralized database expressing parts of the blockchain in a more efficient manner.
As mentioned before, I'm very disappointed by the direction HF24 has taken, and will no longer trust this network and the witnesses running it, until I'm shown the mechanisms used to secure layer 2 with layer 1 consensus.