Wahoo27, I listened to that podcast and I didn’t get the same message you did. At one point Dodson said ADHD is genetic but he never said one of the parents must have ADHD. They obviously must have some genetic component of it but that might not result in having all the genetic components that result in ADHD.
That was my take on it, anyway. I did a brief look elsewhere on the web and saw nothing that suggested one parent must have ADHD.