Ok, so this is one of the reasons why growers should not be doing these tests and actual scientists should, and I will explain why below.
Issue #1 was that he didn't use clones, he did a staged harvest from one plant, so the changes in the THC/Terpenes could have been caused by the stress of the multiple harvests rather than the darkness, or just a difference between colas.
Issue #2 was that he only tested the top of each cola and I'd be willing to bet he would get varied results from multipile colas if he chopped and tested those same colas on the same day. What he should've done was tested multiple colas and averaged the results between them from each stage.
Also, if you look at his results, they don't support 48 hours of darkness like he says they do. The THC% bounces up and down between each stage. If THC production increased from this practice then it wouldn't rise after 12 hours and then drop at 24 hours and rise again at 48. Terpene loss was also dropping at a pretty steady rate of about 0.1% per day.
All in all he supposedly gained 2% in THC over the course of the test but there's no way to know if that is just a variable between the colas he tested or a result of the light deprivation.