I personally don't know too terribly in-depth about the specifics, but in a nutshell, it tries to show you the most relevant job listings considering what it knows about you, which includes location, what site you're looking at, and which questions and technologies you seem to be interested in based on what questions you've looked at (see here).
Since you've participated more on Stack Overflow than here, that probably contributes to you seeing programmer job ads - or maybe there just aren't many sysadmin jobs listed in your local area (would the one you linked be considered "local" to you?). Try a session with no cookies (chrome incognito or similar) to see what it would be showing you when it knows nothing about you aside from location.
To directly address your request - no, we won't specifically prevent programming jobs from showing on Server Fault, because there's a lot of overlap in audience between this site and Stack Overflow, and in some cases (for instance, any of those jobs that say "DevOps") there's overlap in job listings too (and in some cases there just aren't many local jobs to show, so the selection engine needs to work with what it has, and might not show you terribly interesting jobs).