Earlier quoted context omitted.
> The fact is whenever quick upward mobility has been possible anywhere for a large number of people, it has been built upon slavery, colonialism and/or cheap imported labour. Which of these was responsible for China's rise from poverty?
It wasn't imported in case of China only technically. The rural to urban route was "imported" labor that mostly made city dwellers rich.
In addition, these people made a calculus where staying in their ancestral homes meant certain poverty and moving to the city meant immediate increase in income as well as better prospects for the future. The drawback is/was poor working conditions, but I’m not sure they are worse than those back in their an ancestral homelands.