For what it's worth I wanted to share my $0.02, as this topic has come up before with theartofmanliness.com post as well as another forum where a guy did HIIT training/diet/etc and doubled his levels.
I believe that the bloodwork verifying these stories is accurate. However, it's a matter of perspective and context. The guy in theartofmanliness admits that he was living an unhealthy existence, stressed out by work deadlines, eating/sleeping poorly, and perhaps he had gained a little weight. He might've been an otherwise healthy guy who reached an absolute low point in the high 300s before beginning dramatic lifestyle changes.
Another guy I'm familiar with in myfitnesspal.com did the same exact thing with similar results. He admitted he was depressed initially as well and the attitude change combined with dramatic lifestyle changes might've given him the necessary boost to get into normal T ranges for a young guy. Plus he changed over a 6 month period...it wasn't like an overnight type of thing.
I don't know if there is more to the Tim Ferriss story since he is known to be a self-promoter, but it's amazing what the human body can do if one develops healthy habits and implements them over just a number of months. You can lower cholesterol (even with a genetic predisposition), lose weight, gain strength, and I have no doubt, raise testosterone.