Take a look at all the girls who are competing in gymnastics at the olympics. They may all be 15+ but the majority of them still have the bodies of 12 year olds - no hips, no boobs etc. And despite that age limit there hasn't been an overall gymnastics winner over the age of 20 since the 60's. I've seen a good number of my friends reach their athletic peak around the age of 13/14 and then hit the puberty wall and eventually quit out of frustration. The changes to the body at puberty can and do make a huge difference, but some girls change less than others and all hit puberty at a different point.
That said I fully agree that women haven't pushed skiing to their physical limits. We have a lot of progressing to do before that becomes an issue. But when we do reach that point, and if women's skiing turns out to be comparable to gymnastics, we can expect girls to be peaking in their mid teens, with the majority of them hitting puberty and quitting because they suddenly have no chance of being competitive.
For example:
The Chinese national team. All but one of them under 5 feet tall, under 80lbs and possessing questionable passports claiming their ages to be 15 and 16.