I'm a terrible system administrator. Everything I've learned about it has come from necessity because startups. I don't want to be a system administrator and have no desire to be good at it. So I learn the minimum I need in order to get it to do what I need to do and hope that I've done it right.
I might only be slightly better than someone who's new to system administration only because I've written system-level code and understand operating systems and things of that nature.
However a good system administrator understands the entire architecture from a holistic point of view. They know the compiler switches to use, the run-time switches to tweak, the security implications of various configurations and all of the other details it takes to keep a cluster secure.
I often work well with a good system administrator to debug and optimize workloads due to the overlap in our skills. I find this to be the optimal relationship.
Learning and practicing system administration takes away from my ability to learn and be a better programmer (and the opposite is true as well). I don't know about most people but I find I can't be good at both. And I know which one I'd rather be better at (programming).
I don't think the author has hit the nail on the head but I agree that effective teams can't expect one person to manage an entire application from code to managing a secure deployment.