from what i've heard of ssf mm's, i don't think they actually care which way the ssf goes, whereas stock mm's usually have an agenda.
i think it's just the exchanges having mm's who hedge their ssf position in stocks just to provide liquidity to the new contracts.
even so, as long as their is low volume, spreads will be high.
I used to trade the dow futures, and I suspect this will be something like that.