My memories on the Goldmans scale were rather that it was meant to reflect “usefulness” rather than reliability, which meant incorporating how much the figures concerned drove government policy, as well as how realistic they were.

What if China has two speedometers, one real, one for statistics releases ?

It is quite understandable why the provincial figures are higher than the central government once. In the past, the performance of local government officials are linked to their GDP growth. It is natural to report on the high side. The central government has to release believable numbers, and hence the lower.

Statistics in China is for the good of revolution, not to be accurate.