I wonder has the author ever researched on how the U.S give out VISA? or the millions of ways to get on the blacklist of US? For example, mentioning you want to pursue a career in U.S after graduating from a U.S university will cause your visa to be denied. Now that's a lot to talk about.
The VISAs aren't really the point. The point is that researchers outside of China are censoring themselves in order to retain access to their object of study. This has a wider chilling effect.
They are different, but at the same time both visas and censorship are a matter od policy and politics. One could argue that both are damaging country reputation to some extent.
