I'm not sure that is 100% true. I remember there being some talk about men, or women always being screwed by playing 1st/second. I don't think it was that long ago that it was fixed as to who played the first match at night(ie men or women, but it never switched during the tournament.) While one might argue going second makes you marquee, I would think ESPN would want whichever match gets them their ratings(and whether nielsen is right or wrong, that's what ESPN currently uses to sell ads, so they are going to use them for decision making) to go at 7 pm. People know the match starts then. As much as I wanted to watch Delpo-Stan last night, I could only watch a bit of the first set, because they don't pay my bills, I do, and doing so requires me to get up early. Starting at 10 pm, especially in a non-weather induced situation, can cause a lot of problems.
I've never understood though, why there is only one night match? All the courts have tremendous lights.