This follows the usual pattern of expecting your body to adapt within days, against a lifetimes worth of eating. No one in their right mind would think that you could even go from a settee (couch for the others) and run even 1500 metres (try it, let alone a 5000 metres plus). Or step into a boxing ring on no training and do even 3 rounds, most would be finished within 1 round. Why would he or anyone think you could go from A to B with no discomfort. Exactly the same mistake has been performed by Chris Powell who compared 2 brothers on his weight loss programme; one brother was injured so couldn't' do the workouts, Chris put him on a low carb diet I think over 2 weeks. The low carb brother had no energy so low carb was seen as failure - again no adaption (the brother who ate "normal" and exercised just pipped his low carb brother in weight loss). Again similar, the Van Tulleken twin Doctors tested one of them on low carb with no adaptation, which of course under these conditions the carb burner won, surprise. WHY DO THEY NEVER test against an adapted person or allow say a month of change.
This gentleman had at least 2 vital bits of information from Meat Health and Mikhaila Peterson, so he knew about the adaptation.
I have been doing all meat and fish days recently and love it. not ready to go full carnivore as, I am in the middle of my heavy weights experiment still, but I think I might eventually go weekends all meat.
At least people who would like to investigate have some references. Rant over, I will get to my 3 rd workout since being fasted 42 hours - strange what you can do once adapted.