Are they having a full fledged dinner reception or is it more like the Bates and Josh/Anna -- a few appetizers, candy, cake and you're out of there? I think fundie receptions are shorter than most since there is no dancing and often no sit down dinner, though not sure what Jill/Derick are doing since their rehearsal seemed to have actual food -- it would be odd to feed people the night before but not at the wedding itself.
I know I've heard from couples who've waited until marriage that it was better for them to be done the wedding/reception by late afternoon/early evening because that gave them a long time in the hotel to start trying to consummate. Some do that night, some don't for a few days or weeks, but it's better if you're not showing up at the hotel at 10 pm exhausted and then wondering if you should or should not try that night. It's possible that Jill planned the timing this way for a reason.