But my MIL from Mao era has docs from the local officials that's all notarized, as does my wife. The dates might be... you know, not exactly right, but they're close, and importantly they're accepted by both the Chinese government and also other foreign governments for official purposes (immigration, etc).
I think I the article here we're talking about something fundamentally different from the last 70-ish in China. They're talking about people with like no official docs whatsoever, can't get healthcare, national ID card, anything. Very different from China 70 years ago, and very different from even pre civil war China.
黑孩子 and 黑户 were fairly common until the last 5-6 years.
The issues mentioned in the article were prominent in rural China and the lower tier of migrant workers before e-governance innovations along with a relaxing on the one-child policy started a decade ago.
Furthermore, the township mentioned in the article is itself one of those migrant areas in Cape Town, similar to what urban villages are in Beijing and other cities in China.