They don't control for ethnicity, but they study for 200 countries, not just the US. But more importantly -- this has taken place from 1990 to 2020. Have there been big demographic shifts between rural/urban in that time?
In Western countries, yes.
Country Year Urban Ethnic Makeup Rural Ethnic Makeup
-------------- ----- ----------------------------- ------------------------------
United States 1990 73% White, 14% Black, 8% Hispanic | 86% White, 11% Black, 3% Hispanic
2020 57% White, 12% Black, 18% Hispanic | 84% White, 8% Black, 9% Hispanic
United Kingdom 1991 90% White, 4% South Asian, 2% Black | 97% White, <1% South Asian, <1% Black
2011 75% White, 12% South Asian, 6% Black | 97% White, <1% South Asian, <1% Black
South Africa 1991 14% White, 77% Black, 9% Coloured | 15% White, 68% Black, 17% Coloured
2011 14% White, 79% Black, 8% Coloured | 11% White, 77% Black, 11% Coloured
India 1991 69% Hindu, 14% Muslim, 11% Other | 69% Hindu, 14% Muslim, 13% Other
2011 63% Hindu, 17% Muslim, 11% Other | 68% Hindu, 15% Muslim, 13% Other
China 1990 91% Han, 2% Mongolian, 2% Hui | 89% Han, 5% Zhuang, 1% Miao
2020 92% Han, 1% Zhuang, 1% Hui | 88% Han, 6% Zhuang, 1% Miao
Peru 1993 53% Mestizo, 31% Indigenous, 16% White| 73% Indigenous, 23% Mestizo, 4% White
2017 60% Mestizo, 16% Indigenous, 24% White| 74% Indigenous, 21% Mestizo, 4% White> The total 2020 enumerated population of all [331] cities over 100,000 is 96,598,047, representing 29.14% of the United States population (excluding territories)
From: https://en.m.wikipedia.org/wiki/List_of_United_States_cities...
So, for instance, Greater Los Angeles has more than 18 million people by itself, where your source lists it as under 4 million.
Here are the sources-
US: US Census Bureau
UK: Office for National Statistics
South Africa: Statistics South Africa
India: Census of India
China: National Bureau of Statistics of China
Peru: National Institute of Statistics and InformaticsThe best one that I can think of is the fact that rural children probably spend more time outside engaging in physical activity. Even in the US, I know of high schools where a substantial number of the students are working full-time jobs outside during the summer, in addition to doing outdoors sports and other activities during the school year.