Nutrition and chemistry is not learned on the job it must be widely studied and practiced on a regular basis to be fully understood. Last I check DJ was just a meathead - gymrat.
DJ may be train his ass off in the gym, and train others just as hard. He can guide and teach others how to properly pose, and he has the eye for what is right and wrong about a physique. However those taking DJ's advice for contest nutrition prep will usually fail, as DJ himself did has done so many times in the past.