Nope, they, like the MPs in the "digger," were Ptes and Cpls (a few Sgts and, now and again, a SSgt running something big), but they were addressed as "staff."
Strangely enough, I don't recall them as "mean." They had a job to do ~ to get us fit to pass the various PT tests ~ and my memory says that most of them wanted us to succeed. I think (almost) all of us needed some help; I was good at rope climbing but I always had poor balance and I always just barely did the required number of chin-ups. I seem to recall the PTIs (what they were called before we called them PERIs) were helpful and patient as they showed me how to negotiate the balance beams and work, properly, on the parallel bars. But it was, always, run, Run, RUN and I lost count of the number of pushups after about 1,000 in the first week.