I've also heard that AWAC has a permanent ballast kit in their 200's and doesn't impact their operation as badly because most of their operation at lower altitude cities. I've been to some of our stations and they would report that they are out of sand ballast and that may effect how many pax we could take. I bend over backwards to get a JS on and I have never seen one of our Caps to intentionally deny.
If a JS was denied, the reasons may have been valid CG issues. Keep in mind the station gets a load report before the flight and it could list to the station unable cockpit JS.