Really? A journalist posting an edited article that needs further discussion? You don't say!
As for drinking water when training, well, drinking sports drinks whilst training is antagonistic to many parts of physiological endurance development. And the single example of the simple diet appeared to me to be high in carbs and highly nutritious. But really, you'd be hard pushed to find a manual labour job that's more nutrition intensive than the Eldoret training camp. They exercise three times a day, some days including intensive gym sessions, not just jogging around the countryside.
More worth focussing on is the point about slowly building ability over time. At least you won't find a quick-fix to become a world-beater from Jimmy, even if the writer decides to focus on the one, example session. (And probably end up at the physio fairly shortly...)