Easy to implement?

This is just my theory: I think that GFW is currently entering its next stage, which probably includes MITM attack to TLS traffic and some attack specific to websites outside China. I suppose that since everything now is in a "research" stage, they are just trying to see if the technique works and how much it could go.

Disclaimer: I was an user inside China and being blocked from the real Internet. So please take my words with a grain of salt.