There are lower and higher grade levels for Sys Admins. This particular role is for a GS-13, which should be reflected by the required experienced.
He started in DOI as a seasonal post-doc for USFW at a GS-5. My point is merely that the work he was doing then, much less at the end of his career, was both much more specialized and much more intrinsically valuable than a sysad working on this project. And I say that as a recovering sysadmin who's overqualified for this role.
As glup pointed out, y'all have to be competitive though, so this was much more of a comment about the priorities of labor markets than this particular posting.
Regardless, appreciate y'all posting roles like this here.