And that ought to be telling us something! If it is IMPOSSIBLE for a 16 yr old girl to learn a triple-triple NOT because she lacks the talent or the motivation but because of the physics of being a grown-up then the sport isn't about skill but about who has the best genetics and who can prevent nature from taking its course best.
I don't think that's the right way to think about it, or at least it's an incomplete way.
Any highly trained skill, whether figure skating or playing an instrument, often requires intense training from an early age. No amazing pianist or violinist got started after 16-17. It's not only about the physical development, it's also about neural development, including a skill as apparently physical as landing a 3/3. Skaters need to take advantage of the neural plasticity of their brain (which inexorably goes into a steady decline from mid-teens, sadly!) to learn these tough moves, which require fine timing and coordination of the different parts of the body. Physical attributes like power and flexibility alone definitely wouldn't get you there.
Besides being able to learn more and faster, children have over adults the advantages of not being afraid of learning new things, and also healing much faster when they do get injured. It's much more dangerous for Joannie Rochette to try to master the 3-3 at her age, than it is for 14-year-olds. An older skater has slower reaction time, is more prone to falling, and any injury is more likely to affect a whole season.
That said, obviously even children aren't immune to injuries, and obsessive, repetitive training of one or a few elements can lead to long-term injuries, like Tara's hip, Miki's shoulder, Yu-na's back/hip, etc.
So in order to protect the sport and the athletes, skaters, their families, and their coaching teams just need to be really aware of the various risks, and balance them as well as they can against acquiring excellence in the sport.
Also, the reason we don't talk about guys is because they usually develop their full technical prowess later so young teens almost never appear among the elites. Their bodies don't hit a puberty wall the way women's bodies do, so they can continue adding difficulty to their tech content. Female skaters, on the other hand, rarely add new tough jumps to their arsenal after 17-18, and it is also very dangerous for their mature bodies to attempt to learn them (like Joannie is doing now).
ETA: To complete this last thought, I want to relate it back to the age limit. Although there are the occasional talented 14-year-old guys who have all the triples save the 3A as well as good presentation skills (like Patrick Chan at 14), they cannot compete with top senior men who are doing 3A and quads, so the issue of sending them to international competitions before 15 almost never comes up. So the age limit in men's event doesn't have nearly the same impact as it does in ladies'. Given the arbitrariness of the age rule (why 14 or 15, why is July 1 a magical date, why inconsistency across competitions & countries), and the difficulty of enforceability (how do you prevent a rogue federation from fudging birthdates of young, obscure skaters that nobody outside has ever heard of?), I think it's clear that the age rule is not a good idea and something else needs to be thought up.
If the scoring rules of figure skating were changed, such that 14-year-old girls have little chance of competing with mature women (e.g. by placing a greater emphasis on artistry), then there would be no need to decide whether someone like Rachael Flatt who missed the July 1 deadline by 3 weeks should or shouldn't go to the senior WC. And there would also be no incentive for some federations to cheat, and others to feel cheated. The age rule would then become redundant as it has been in the men's event.
That's the direction this is going anyway! There were more 3-3's in the ladies event at '06 JW than there were at the Olympics in the same year. And the technical content of the '08 JW among the top competitors will be similar in difficulty to the top WC competitors. Don't forget that Caroline had the highest TES in the SP and the second highest TES in the LP at the GPF, even though she's hardly considered to be an especially good jumper.
