Good post, but I think, like many, you've taken this line at face value.
Strachan was an excellent man manager and part of his method in this was to take pressure off of his players. He never came out and said that the players had a flat performance, or that they were poor. The eugenics line became the story, and nobody talked about how we just weren't at it against Slovenia. We were poor and the defending at both Slovenia goals was dreadful, but even now the narrative of that game is defined by us just not being tall enough as a race. It was a clever distraction designed to take the pressure off his players. That's all. I don't believe Strachan believed a word of it.