From what I understand, sx themselves is acting as a market maker to bring some initial liquidity but still with odds that have quite some juice on them. With feels turned off right now, sx is pretty much betfair with no commission but at the same time with a limited number of users. It's the classic catch22 for everything that tries to be a betting exchange. liquidity is needed to bring users but users are needed to bring liquidity.

I never even heard of UMA, good info to know they are using that.