Chinese GDP is suspiciously stable at exactly the same value for long periods of time, and doesn't seem to correlate with other statistics that usually do correlate, like electricity usage.

IIRC it's not even a secret that China's GDP stats are useless. It's a problem the government has officially admitted to. As a sibling comment notes, the issue is that they aggregate stats from regional governors who are incentivised to tell the party what it wants to hear.