Many in the mid/top in China are in the Communist Party or mil. With that comes a set of rules. That foreign travel and education, a good home, nice school, safe food, access to a lab, staff will come with a lot of rules.
A mid ranking mil uniform to work no matter the job, tasks or position. Surrounded by orders, uniforms, rank. No freedom, any comment gets reported, been denounced or reported on is an every day risk.
The freedom in the West for further education is to learn and bring back ides, tech, trends, insights or spy on Western campus dissident or faith groups.
Long term China can only buy into the West and hope the in house Western tech is advanced enough to get a few decades of advancement. Before needing to buy up the next Western brand.
A call back of people to China does not really help China. China is full of mil and party members who all know how to serve the system.
The West has its growing, failing, bankrupt churn of the very best ideas with freedom to fail, freedom to talk, freedom after a conversation, freedom to publish, freedom to find funds, freedom to seek the best teams, to work alone or on campus, or be part of a large company or have a huge campus, freedom to read any book or enjoy a movie. To find the very best graduate or PhD without needing political approval.
Thats is what makes the US so attractive to China. Ideas flow in the West without party political bans, exclusion, loss of education, loss of healthcare, only been given really bad accommodation, loss of Communist Party privileges.