He's likely is referencing the fact that back in 2012 the Chinese data was just from Shanghai. This was not a secret -- it was also listed as just being from Shanghai. And they took first or near first in literally everything. Shanghai, of course, is a city (a rather large one at a population of 24 million) but not China as a whole.

There was extensive media coverage calling China's results completely fake and unrepresentative. The most recent data from 2015 (what I referenced) tested China as a whole. Their rankings declined, yet they remain far ahead of the US in everything except reading where we are a tiny sliver ahead of them. This received minimal media coverage.

This is a general issue when media. When the media emphasizes one issue strongly, only to give minimal coverage to the revelation that they were wrong (the implication of the coverage was that China would not be a world leader if the data were 'real') - it leads to a misinformed populace.