After reading the Why page, I still don't have a concrete notion of what this is. So I'll jab a few questions that might help me make some sense:
First question is about decentralization. What is off-chain relay in this case? Is that a centralized part of the system? Are there centralized parts of the system?
Can this be used to implement more robust margin trading? To my knowledge, only centralized exchanges/brokers currently exist for margin trading.
What settlement speeds can be expected?
That's it for the questions. I don't want to retract from them, but I'll mention that the site doesn't work well with Dark Reader: all theme generation modes, except static, render most of the text invisible.