I think he is correct, but there are caveats.
There are individual runners who train as hard and as focused as Colorado. As a group, Colorado does it better, and with American high school runners the program develops.
This is little different than Arkansas back in the 80's and 90's. Arkansas had talent, of course, but they trained harder than we did (I was on a decent Division 1 squad with lots of focus on high level academics, and knew darn well that 60 miles a week was not up to par, even if it was fine for my team). Arkansas had a few more foreign athletes than Colorado, but their guys were developed well, too.
I note that Theroux mentions how early in the year they start and how well prepared they are. Performing insane workouts and hitting high mileage starting in September doesn't cut it, as it leads to fatigue, injury, and a lack of performance in November. Consistency is important - what you time on the time away from campus really matters. The mental aspect matters, but let's face it, if you can run 18 miles at altitude at good pace and be relaxed and controlled, well, it is no accident that Colorado finishes their races so well.
I am not sure if Division 1 running makes sense for those with significant academic aspirations. It is a different world today, with a much earlier race for internships, the right professional focus and the right credentials - a shame, really. But make no mistake about it, I admire the guys at Colorado tremendously. As with the Arkansas teams, they deserve the accolades thrown their way.