So I cannot speak for anyone else or any other school, but my teacher holds back on creativity until a student has learned a great deal then he begins to let out the rope on creativity piece by piece. The funny thing however I find not that I have been granted permission for a couple of years, I find I always gravitate back to the simplest of movements, kind of least common denominator theory. This is not to say I don't do a few things different because I do as my body size, shape and performance are different from that of my teacher. I also have found ways to practice drills being creative, but I do not vary too far away from the foundations of my art. Why should I as my art, Wing Chun, has been around at least for some 100+ years in it's current state and likely closer to 300+ is some form or another as well as practiced throughout the world. So if it isn't broke, don't fix it.