There is no question that topics overlap. Further, many of us wear more than one hat, sometimes very many more. For those of us who are also involved in the management side of things a question such as this one may well be relevant to our jobs but it's not a system administration issue.
Let's take things just a little further. As part of my job as a sysadmin (I'm the entire IT "department") I also write code, so should I post code questions to SF? No, they belong on SO. I also change the paper towels in the gents (because everyone else is just too lazy to do it). Should a question about a jammed towel dispenser be posted to SF? I suspect not.
Equally, I doubt those on the security site really want questions about how to best create a set of firewall rules to implement the policies formulated by management.
If you are one of those who's job takes in more than one of the fields covered by the different sites you simply have to get involved in each of them.