Sounds like he realized that it's BS.
Finally, this year marks the return of my endurance. After having built a 20-year base I fell into the trap of thinking there might be a free lunch. I went against everything I had learned over those 20 years because the argument and its presenter was quite convincing, and I was susceptible to the easier way, the cure-in-a-bottle way, and I wanted the experts to be wrong. I went into it headlong, and received enough positive feedback to swallow the hook rather than letting it set in my lip. Emphasis on short-duration, high-intensity work didn't strip endurance from me right away, rather the opposite occurred in the beginning. However, 18 months of nothing but short, hard efforts did "cure" my endurance. Despite an ability to go hard for durations up to three hours in length, "hard" is a relative term that didn't equate to fast in my case. I couldn't recover quickly from such efforts nor did I improve even after I balanced short, high-intensity work with longer, low-intensity training sessions. I realized that if I didn't spit up the hook I'd be stuck on the low plateau I'd chosen for the rest of my life. While some are content with mediocre performance - especially if someone keeps telling them its "elite" - I expect better of myself and I'm willing to suffer trying to achieve it.
What Twight went through is what a lot of people have gone through, including some on this board. I count myself in this camp as finally starting to see through the hazy claims of internet fitness gurus. Endurance is trained through endurance. Speed and power is trained through speed and power. The different qualities often compliment one another depending on past training emphasis. Depending on the sport, and where the athlete is on their competitive calendar, the balance of the two should shift.
Nothing but high intensity circuit and interval training is poor programming at best. Nothing but long slow distance is poor programming depending on the sport. A mix of the two depending on the requirements of competition and where the athlete is in the training cycle is intelligent.
Crossfit just so happens to be epically stupid when it comes to the high intensity stuff. Mike Boyle, for all of his faults- and I am still a marginal supporter of his, noted on a Strength Coach podcast that if Crossfit was built around solid screening, progressions, and proper coupling of movements, that a decent argument could be made for it.
Then again, it would be like any other workout programmed by guys like Boyle, the Cressey Performance metabolic finishers they use, Alwyn Cosgrove etc. It wouldn't be Crossfit, because it would cease to be so dangerous.