However, the idea that a direct supervisor will by design know when to violate company policy in order to safeguard an employee is not feasible.

This just is not true.

Any halfway competent safety policy, BY DESIGN, allows anyone to stop any work whenever they reasonably judge that work to be unsafe. If that company doesn't have policy designed as such they should be held criminally liable for the inevitable harm that will result. There is no excuse for any supervisor to not put employee safety at the very fucking top of their priority list, regardless of policy. Anything less is just making excuses. Anyone that puts company policy above community and worker safety deserves to bear the responsibility of their decisions or lack of action when in a position of authority. No company policy is above basic humanity.