Yes, the labor surplus was caused by China's family structure. In China women married as teens and started bearing children young.

In Northwest Europe, women married when they and their prospective husbands had saved enough to form a new household, typically 24 to 27 years of age. That is several fewer children per woman.

It was also self-balancing. When population was high, wages decreased, so women married later, so population decreased in the next generation. And vice versa.

In China, childbearing was not regulated by economic conditions so the population was controlled via famine, which tends to bring riots, banditry and so on with it.