And on top of that, it sounds like Microsoft ditched most/all of the proof-of-work, because the nodes are trusted and the proof-of-work increased transaction times. So it sounds like whether Coco is actually a blockchain or a distributed database which has been branded as a blockchain because blockchains are FotM, is debatable.

We tried to address several distinct concerns with Coco: scalability, latency, confidentiality and governance. Scalability and latency are determined largely by the consensus model of the network. Our intent with Coco is to make consensus pluggable so that each network can make its own choices (via the Coco network constitution) about how to run their market.

I agree with you that the branding is tricky, in part because the dominant term "blockchain" is describing a specific data structure. The key point we wanted to convey with Coco is that we are trying to enable secure, performant, multi-party computation. We think there will be many models for this over time as TEEs come into wider use. "Blockchain" is just one of them.

In the demo video they explicitly say Coco is not a blockchain.

The part of a block depending on the hashes of its ancestors seems very useful for tamper-evidence, which is useful in many applications if you can handle the data model & volume. Being able to definitively say who changed what and when is worth a lot if you have to maintain data which could be used in court and a distributed ledger, Merkle tree, etc. is more predictable and much cheaper to run if you don't have to maintain mining-level infrastructure.