Person experience:

Despite larger grip strength the average height of rural EA male are still below 170. Because they are so poor that they can't afford enough protein, almost zero understand of exercise. Most importantly, they face lots of stress for study. For instance, lots of them would sleep only 3 hours per night. For the reason that they hope to exchange their hard work for a richer future (go abroad or live in EA cities). If they can't they cannot change their fate for themselves.

I always admire their hard work as they eat 1/3 of my calorie but achieve a top notch grade. And I always thankful that I was born in a city.

The only advantage the city population have is adequate calorie that can be accepted by scientists, and they reach 175. However, a vast majority of city population lack a list of certain nutrition in their diet, would sacrifice height growth opportunities for study. And as you mentioned, sedartory lifestyle due to culture. Moreover, a poor understanding towards workout. LoL, I don't recommend protein shake, however some people even refer it as steroids.