It might be related to the reportedly recently obtained subsidy approval for the MIC Model 3, of around 24,750 yuan ($ 3,500). It's possible that Tesla waited on deliveries to get all the bureaucratics done.
Below we attached a Twitter post from Jay in Shanghai, which shows images of Model 3s on a carrier.
The EV Stock Channel recently estimated, using the growing number of MIC Model 3 on the parking lot at the Gigafactory 3 as a base, that the production rate between November 29 and December 5 increased to over 40 a day (1,250 a month).
Other unofficial sources say that as of December 9, the production already reached 1,000 units per week (some 4,000 per month or 50,000 a year).
Well, now we are just waiting on the reports of first deliveries of MIC cars.