After seeing this thread I called them to ask why the ES is not listed in the inter-spread lists, and she said, "It's just not something we considered, we figured everyone would do the conversion in their head." I suggested they just list the darn thing on their website, to reduce ambiguity.
Yea, it can be obvious for many ppl, but there is a lot of ppl trading something else or just new to futures, so it should be clearly shown. but call them - that's the spirit