China has state run Telecom companies providing all the eyeball access, so it's relatively straightforward to ensure outside connectivity goes through the great firewall.

Hong Kong has multiple private companies providing eyeball access. It would be far more difficult for the Chinese government to get all of their compliance. If they just wanted to get traffic information, it would be far easier to just collect a statistical sampling collected from flows data on core routers for general info or to monitor specific IP's using rulesets without the massive undertaking needed for always on firewall capabilities on every single packet.

Back in October the HK ISP association put this out [1] about how bad it would be for them to be moved towards a GFW model, so I guess they're somewhere closer to Western style access requests still: https://www.hkispa.org.hk/139-urgent-statement-of-hkispa-on-...

It is definitely not, However, a surprising (to me) number of people in HK use WeChat for nearly everything, so...

It isn't behind the Great Firewall, but it is behind an increasing number of government controlled boxes that could be turned into the Little Firewall. There are many direct fiber paths into HK that go directly to big companies and it would take time to bring them under control, but it would take only be a matter of time.

The other aspect of the Great Firewall is the alternative ecosystem inside it, and the censorship system embedded in weibo etc. It will be interesting to see if surveillance capitalism apps like Wepay and Alipay suffer a setback in HK in the wake of the protests. Cf https://www.bloomberg.com/news/articles/2018-05-24/alipay-s-...