[Tsagadai]

It could be that further up the network they are dropping HTTPS packets, or that they plan to in future. It isn't unheard of to simply deny encrypted protocols at the ISP level for a period of time and I could see China doing this in some areas while simultaneously forcing common sites and apps to have functional unencrypted versions to minimise commercial disruption.

[arountheworld]

The EU found a way around that with "content filters" - basically anything you upload will be sent to a government controlled body for inspection. This works fine with encryption and there is no need to ban math.