The correct answer is that they're pretty close.
Rupp's jog 28:38 tonight was at 2:52 per km pace.
In his 1:26:47 30k, Mosop ran the first 15k at 2:55/km and the second 15k at 2:51/km. This should help to show just how little of a factor Rupp is likely to be on the world stage.
This race was a total embarrassment. Kenyans who see the USATF results must think it's a typo, but indeed 28:38 takes a win at our WC trials.