To be fair, he might have decided to create this documentary precisely _because_ he has this mutation (I'm not saying that that's the reason why his cholesterol is low, or that this is good/bad), and therefore reacts abnormally to this diet.
Before you brush me off, I am aware that high serum cholesterol is a predictor of heart disease. However, a more plausible explanation is that the body manufactures more cholesterol to fight an impending problem.
See e.g. http://blog.sethroberts.net/2011/04/12/statins-reduce-choles... for references.
(Analogy: if you can only look at the drain of a sink, you might conclude that water is likely to cause soap, because clean water almost always comes down before soap water does)