I couldn’t tell you to be sure. But, it’s worth noting that all of the upgrades and improvements rolled out on NA cars were always shown in the China cars first.
The added trim to the doors, car colorizer (from the UI to much custom exterior wraps), and the rear privacy cover in the trunk are all examples of features first debuting in cars from Giga Shanghai. So with that, I wouldn’t doubt that the Chinese cars have had the glass since day one. As far as rear windows having the 2x glass I don’t think any Tesla currently has that from either factory yet. But, if they do start putting 2x glass in the rear I wouldn’t be surprised if Giga Shanghai starting doing it first.