Given that most jobs in the US pay 10X or more what the same job pays in China, they are probably concerned that trips to the US will be one way.
Aslo, perhaps slightly off topic there are loads of Chinese crossing the Mexican border to take advantage of the recent open border situation.
60 minutes clip on that https://youtu.be/M7TNP2OTY2g
As a Brit I watched that in slight amazement and thought the Dems are going to lose the election if they keep that stuff up, which of course came to pass.