some people are happier in a high performance environment with employee churn, when it means having more talented coworkers
It means having coworkers who are constantly in competition with you for survival. It's a nightmare.
Different people can have wildly different expectations for a work environment, and wildly different tolerances of social discomfort.
I'm not sure it is really correlated? It causes a lot of the high-performers to jump ship pretty regularly too - the company is perfectly happy replacing an expensive veteran with a college hire
High churn doesn't necessarily mean low average talent, especially if the skills you need to be a high-performer are not specific to any one company.