Salazar continues to be very focused on Rupp's sprint mechanics, but of course the point of all that isn't to become a sprinter, it's to be able to maintain good form when trying to hit top speed at the end of a distance race.
I'm sure Rupp is coming into this 800m with a bunch of form keys to think about over the last 100m, when he'll be trying to hit top speed in a fatigued state. He will then get a chance to see which keys he executed properly and which he didn't when he and Salazar review video after.
You could try to do something similar in a workout, but racing an 800m seems like a sensible way to go about it.
Why don't other 5000-10000m guys try dropping into 800s from time to time? No idea, but they may start if 2013 goes as well for AlSal's guys as 2012 did.