The dark factory setting is mainly for the component manufacturing and the "skeleton" of the aircraft. Final assembly still need human hands.
As per the news article:
"China has more than doubled the production efficiency of stealth fighter components in a “dark factory”, where autonomous vehicles and AI-driven machinery operate nearly 24 hours a day.
The process once required employees to monitor its round-the-clock operations, but the plant can now produce the “skeleton” of an aircraft in near darkness, according to the official Science and Technology Daily."
"The plant is also equipped with intelligent scanning systems and robots that can inspect products and quickly generate reports."
"It has also reduced the hours of human labour needed to operate the plant by more than 80 per cent – although workers are still needed for the final assembly of the planes."