In a lecture to senior business executives on Dec. 16, Renmin University economics professor Xiang Songzuo, said that a “very important institute” in China estimated that China’s GDP growth for 2018 should be about 1.67 percent or even negative, and not the statistics bureau’s official figure of 6.5 percent.

https://sinoinsider.com/2018/12/politics-watch-xis-reform-an...

The numbers may not be super accurate but if you've ever been to a big city in China in the past decade you would have witnessed circa 10% GDP growth with your own eyes.

I don't think anyone thought they were accurate, what mattered was the fiscal policies the Chinese state bank enacted regarding the value of the renminbi.