Accepting at face value the claim that "every job site manager on earth" really can identify the "unsafe employees", then these managers are negligent and thus culpable for the failed outcomes.
An infinitely better course of action is to ban all known-unsafe employees from operating in the risky path. Workers who unnecessarily put themselves and everyone else in jeopardy have no business being in the path.
With that said, I'm highly skeptical about the veracity of this claim. Human behavior is fundamentally unstable, oscillating in the continuity spectrum between stable and erratic. However, the amount of variability for a given individual tends to be stable, which may be what you are saying a good and effective manager should be able to catch.
Regardless, humans are wetware and fundamentally error prone. Best to account for this element of our nature in the larger system design.
I guarantee you that every job site manager in the WORLD can identify the unsafe employees, even if they're doing 'everything by the book'.
Some of it can be designed away (two-hand tools for example) but some of it is basically inherent.