One way of looking at this is to ask what it "means" if a lot of players leave early for the NFL as the answer is essentially these same. If the goal is "career enhancement" (we never really know unless we can read minds) it's a "good thing" in the long run albeit disruptive in the short term.
For position coaches and so some extent coordinators who want to be HC candidates at some point that road can turn into a "check the box" career pattern. When I've read about coaches who went this route it was about mastering positions (remember Lou Holtz who coached DBs to learn the job starting with zero knowledge) plus ideally seeing how good coaches with different styles/idea ran their programs (could easily be a lateral move).
"Bad turnover" are those losses than seem like lateral moves with no obvious career benefits - remembering that coaching isn't like the military (up or out) ... there are lots of good reasons for this moves at times generally not covered by the press (roots for retirement, getting free tuition for a family member or some other school benefit etc)
To me is about pattern on and off the field. A certain amount of turnover is reasonable but if it looks like folk are "bailing" (no good reason) it's pretty clear there is some kind of management problem either in recruiting or the operations people or process. Don't think that is a ND issue at the moment