The point is that educating the best minds of the world and then expelling them to their origin countries is not a wise practice.
It is a very wise practice from a soft power perspective.
China also restricts democracy and access to the internet, but that's not to say the US wouldn't be harmed by a move in that direction. China has different strengths and weaknesses; the US would be ill advised to give up its own strengths.
The point is that Top Chinese PhDs got degrees from Top us schools are forced back. Not that immigration are needed for China.