I can corroborate that. I visited China in August 2019 and had terrible internet performance to sites outside of China. This was both with mobile and wifi at the homes of two friends, one in Heilongjiang and the other in Beijing. When I visited in February 2015, it was much better. Both times, I was using VNC on the company VPN. This does not use much bandwidth, but is quite latency sensitive.
GFW has some different settings that they use, similar to “ThreatCon”… if civil unrest is happening, its working is changed. During party conventions, they change it too.
So when a foreign visits China, that experience might be different from one visiting during a different time period.
Also, some hotels that only accept international guests backhaul traffic thru Hong Kong, providing an experience that looks much closer to US/Europe broadband.
Rubens
Note, of course, further, that "the GFW" is not a single appliance, nor
even a standard, common appliance. There are very different "GFWs" based
on which link you're looking at, which telco it is, etc. Indeed, usually
traffic to Hong Kong is effected much less by the GFW than other links
(though still passes through *a* GFW). I've also found traffic destined
to Khabarovsk (depending on the routing) to pass through GFWs which
rarely cause issue.
Matt