I did not read the article. I am guessing he is one of the worst, using whatever statistic they are looking at.
To me, he gets one for one on one defense, he gets another one for not doing stupid stuff (like Chriss and Jackson, for example), and he gets one for rebounding. You may disagree, but I consider rebounding to be a part of defense.
Bottom line is that he sucks defensively, but he could be worse (especially in one on one situations), and he could be doing stupid stuff.
I've said this many times, but some people had unrealistic expectations. People proclaimed him to be a David Robinson, and dismissed obvious issues with his drive and defense, proclaiming that he has the body of a Greek God, and he will be a good defender when he starts playing his natural position. Anyone who had one ounce of objectivity is not surprised by his lack of drive and defense. He never had any drive, aggression, or defense. Not in high school, not in college. He wasn't magically going to get aggressive, find his drive, and start playing defense the day he stepped onto an NBA court.