Depends on genetic skill level and strength etc I think. Some girls, like Monica Brant started training for them and mastered them in a few years. I personally have been doing it since childhood, 20 odd years and mine still look horrible could be improved 
I agree, CQ. Depends on the person. For me, it took about a year to pick up most of the basics (round off back handsprings, standing back tucks, aerials). But, that was working one-on-one with a coach 3x/week.
I also see the author of the thread's point of view about figure. I think it started off as something good, ie, fitness physique without the routine. However, it has morphed into something completely different: a competition where bone structure is the primary judging criteria.
And, I have known trainers who have taken girls that never really trained, put them on anavar, clen, GH, test site injections, etc.............and they swept all the local and regional shows...........for a short time. After 3-4 shows, the drug use really started to show (along with the lack of consistency in training), and the placings started to drop. Then? It was time for the trainers to pick another scrawny girl and start from scratch.