And, at least two years ago, could be trivially worked around if you bought appropriate SIM cards in Hong Kong, which - apparently completely legally, and with cooperation of one of China's telcos - gave you completely unfiltered access in the Shenzhen area.
Sadly, I learned about this only a month into my stay in Shenzhen; before, I was playing the BPN cat&mouse game.
China seems to have a weird dual stance about GFW. I even heard rumors that companies could pay someone to get a legal, unfiltered link.
A hong kong SIM wouldn't work well in Beijing. Also, I noticed hotels in Guangzhou had GFW-free internet, something that would never happen in Beijing or Shanghai.
I've always been surprised by how decent the internet is in Shenzhen most of the time, but I have still had a lot of blocking on some trips. I barely used my VPN on my last trip because nothing I used was blocked. This hasn't been the case when I've even been in neighbouring cities like Dongguan or Zhongshan.
You can get Hong Kong SIMs that have data plans that can be used on the mainland without extra roaming fees. They're more expensive than regular data plans.
Companies in China definitely can pay to get a fast VPN to get unfiltered access. Especially western companies & tech companies do this as you really need unfiltered internet access to do any productive development (an even for non developers, management is using tons of web tools hosted outside of China so they also need VPN to be able to do their work).
This is still an option, and last time I was passing through the HK airport I noticed that a shop next to immigration was selling very reasonably priced data bundles with that kind of dual-network SIM. Highly recommended for those who only stay for a week or two.
Sadly, I learned about this only a month into my stay in Shenzhen; before, I was playing the BPN cat&mouse game.
China seems to have a weird dual stance about GFW. I even heard rumors that companies could pay someone to get a legal, unfiltered link.