I haven't read the whole thread, but I agree that the interview was better for the question you asked. Most journalists shy away from asking tough questions, so the fact that you did not, and even managed to do it in a respectful manner, is clearly positive. Obviously, it would have been great to get a follow-up, or to ask the same question to Alberto Salazar, but since that wasn't going to be allowed, you probably did the best you could under the circumstances.
Let's also not forget that athletes, clean or doping, regularly face tough questions. Lance Armstrong held countless press conferences during his career where he faced questions by some of the best and most critical sporting journalists in the world, including David Walsh, Hajo Seppelt, and others. That never lead to anything - except, with hindsight, to confirm the degree of deception.