I think it's more accurate to say that good developers need to have some level of systems expertise which probably means OS & networking fundamentals + practica

I think it's more accurate to say that good developers need to have some level of systems expertise which probably means OS & networking fundamentals + practical Linux experience. This is because you need to have some understanding of how your program will execute on (or across) machine(s), and some know-how to get your program up and running on a real machine available to users on a real network. Whether you need to be an expert in the latest best practices for managing a fleet of servers compliant with whatever regulations, that's more for the sys admin (though it never hurts to learn more, there's just so many things we developers could spend our time learning).