All of the things you listed are ops topics. But sockets are a programming concept.

I would expect a person with 10+ years of Unix sysadmin experience — but who has never programmed directly against any OS APIs, “merely” scripting together invocations of userland CLI tools — to have exactly this kind of lopsided knowledge.

(And that pattern is more common than you might think; if you remember installing early SuSE or Slackware on a random beige box, it probably applies to you!)