Just because you don't see how it slows things down does not mean that it does not slow things down. The web in China is slower than the web in HK. Why? I don't know precisely because I don't have access to the GFW of course. Think of it as a funnel, the communication has to pass through the funnel so that the RST (or whatever) can be inserted. There's only so much BW in to and out of the funnel - so the traffic slows. The very fact the filtering happens must insert some delay.

Have you tried the web in China?