Have no opinion on Cain or Salazar. But if you wanted to beat blood profile testing and analysis later on wouldn't high school be the best time to start? Achieve ideal just at limit hematocrit/ test/ hgh, etc levels through doping while not subject to routine outside testing.
Then smart micro dosing later on will still match your "natural" blood profile taken at beginning of wc career?
Plenty of high schoolers in other sports (football mainly) manage to get a hold of steroids and use them to their advantage. When I was in hs, there were a lot of steroid rumors concerning a champion sprinter in my state. He was a super nice guy but his appearance, injury history and flatline performance in college seem to be consistent with the rumors. I don't think distance runners are any more ethical than sprinters or football players so I would imagine some successful hs distance runner has helped himself out.
Again not accusing any particular hs track athlete or coach of doping. Just pointing out it is far from out of the question.