I don't see why an employer should be entitled to know anything about an employee's health (mental or otherwise) outside of what a doctor might order as reasona

I don't see why an employer should be entitled to know anything about an employee's health (mental or otherwise) outside of what a doctor might order as reasonable accommodation. Employers "managing risk" sounds like allowing them to exclude people with mental illness or other disabilities. Maybe that's not what you mean, but I believe that is what employers would do.