I could be wrong, but I think they're referring to all the middle class Chinese who were using housing as an investment vehicle (cause that was a common thing in China to my understanding).
I did not know that, but I don't think it matters. If you have 3 houses, even if they're worth less, you have a place to live and the possibility to house 2 other families/even more. That is wealthy in my opinion, and it doesn't really matter how much it "values" at.
It matters when all 3 of them are mortgaged and the mortgages are now more than their actual value.
(Before you blame the buyers for being dumb, realise that due to cultural context and other factors, pretty much the entire middle class is in this sort of situation).
Boo hoo, I own one house and have all my savings in it. Go sell 2 of them and live in the 3rd, let someone else use them without needing a parasite middleman between them and housing.