in my opinion, the shoe you wear is not so much about the distance you run, but more about the pace you are running at. if usain bolt can somehow sprint a whole marathon without busting his achilles, there's no reason not wear his puma sprinter spikes.
as for the vaporflys compared to other racing flats, if you had two people of exactly equal speeds and put them in a 100m race, a person with Streak LT is obviously more likely to win than the guy wearing vaporflys because Streak LT performs better at higher speeds. in my opinion, what makes vaporflys so great is that they are "energy efficient", meaning that they will fatigue you less as you run at the cost of not being the speediest shoes you can wear. so when it come to your harvard example, correct me if i'm wrong, but that was a cross country race in the snow, correct? when people run in cold, snowy/rainny conditions, they automatically run slower due to instinct, safety, they're not as warm, etc. because they were running at slower paces, the benefit of vaporflys reaches or goes beyond the benefit of the Streak LT. i believe this to be the reason why they decided to run with vaporflys. they're harvard students after all; they probably made a pretty educated decision.