This relates to the idea that certain hours of your day are more valuable than others. If you want to spend your time wisely, you should first make sure you're wasting the most valuable time. If you're a coffee drinker, the hours after drinking it are probably the most valuable of your day - when you're most motivated, productive, and focused. So you should use those hours for what your value most, whether that's writing, learning, working out, etc. And then save other activities like cleaning, watching TV, or commuting for times when you're not feeling so sharp.
So the article makes sense in recommending different activities for different people - it just reflects their priorities.