TaskBoy

I do a lot of my own drywall work but hired a crew to do a room with some cathedral ceilings. On the head high and lower areas, I saw that they used a knife to shave down or feather the semi set-up drywall mud so it didn't have to be sanded as much later. This was very cool as it cut down on the dust that would have normally been produced. I tried it myself on some patches in another room a few days later. I was able to feather the set-up mud's "heavy edges" smooth and in other spots, pushing with the knife's edge, shave down the excess to feather it. I had some spots that were smooth enough to texture w/o sanding and others that barely needed any sanding at all. Is this a widely accepted practice for pros or were these guys onto something sort of unique? I've never seen it on any online drywall tutorials.