The US is worse for Chinese scientific & engineering talent in many other aspects even if it’s better in work life balance. The way to address the talent competition isn’t necessarily by directly attacking 996, although I do think 996 is excessive.
For example, how about paying people more? How about addressing ageism? How about guaranteeing job security for competent people? How about putting China’s vast service labor force to work helping with child care, house cleaning, cooking, etc. for these specialists? How about providing free housing in quality districts?
Life in the US despite better work life balance isn’t really that great in many other aspects, and that goes especially for Chinese who are blocked from working in sensitive industries and discriminated against for leadership positions. Not to mention the dating struggles and loss of social prestige in white dominated societies. China could do more to work these angles to retain workers rather than just promote people to work less.
At that level of competence you're not interacting with US lower working class people. You probably have a nice home in a gated community. Another problem i see for China is the generational leakage of talent, its not only Chinese talent that China is losing they are also losing the next generation, the children of those highly talented couples. So not only is work & life balance better in the US, but also elite reproduction is better because if you have money one can easily buy the services for ivy league entry for your kids. Also those kids will have less competition in the US compared to the ocean full of sharks thats China educational system.
But i can still also remember a time when Silicon valley and US tech in general had 996 or even worse 100 hour workweeks and doing 100 hour work week was a badge of honor for engineers. But US tech sector around early 2010s decided to change up this work life balance situation. I can still remember the wave of articles of big tech company x has unlimited off days etc. US big tech saw they were haemorrhaging talent at an unsustainable speed. Chinese government did observe this hence the anti 996 messaging recent couple of years.
Since US big tech did this move you also saw an explosion of open source projects and contribution in the western tech sphere. Tooling like docker, kubernetes things that allowed small to high tech companies to scale their services. A wild explosion of new programming languages(rust, zig, c3, odin etc). Im not sure if the culture change in silicon valley was the cause but i think it does correlate a bit together with github helping facilitate collaboration.
I'll be honest as a tech worker i'm behind a screen from like 8:00 till like 23:30 but i only work from 8:30 till 16:30 outside that range its hobby coding projects or relax gaming time.