Re: difference with other sports

For one thing, you are right that most of the time, peak ages will probably span several Olympic cycles. Female artistic gymnastics should not really be an exception - I think perfectly viable that a gymnast, even in this era, competes 2 Games in all around and national team, and 3 Games in their best apparatus. Of course, the even longer lasting of Caslavska and Latynina is probably no longer possible.

And yes, rhythmic gymnastics, figure skating and diving tend to have the same biases that artistic gymnastics, though to a lesser degree. They share many of the features of control and agility; but I think part of the reason why all of these start their peak age almost at the same time as artistic gymnastics, but also end it way into the 20s, is the particular needs for a very finely tuned equilibrium - rythmic gymnasts and figure skaters (almost) don't leave the ground, divers (almost) only use one direction of movement... artistic gymnasts have to throw themselves in all directions... it is always an advantage to have the youngest ear and brain possible, at least since you're 8...

Horse-riding doesn't have a specific advantage for the young - it does for the light. As long as the jockey is light, there is an advantage; but that can just as easily be fulfilled by a 4ft10 35yo than by a 4ft10 12yo. What is more, in some horse-riding disciplines, where it's not the raw power of the horse that is important, but their ability to listen and obey commands, the advantage of light is also matched by the need to be "a good rider" in the sense of mutual understanding and trust between horse and rider.

Table tennis is more physical than you seem to believe - but admittedly, it's not so in the degree of most Olympic sports. Sychronised swimming, though, while style-driven, is very much a strength sport: to do all those moves and figures in the water isn't "natural" or easy - sychronised swimmers have to be very strong, esp. in their legs and aerobic capabilities, even though they also have to be graceful. Shooting, both bow and arrow and firearm, otoh, prove your point in that they are usually sports where an Olympic-level athlete can reasonably expect to compete more than twenty years of Games - in Beijing, we still had people who had competed under the Soviet flag...

No idea about American jockey regulations - but I know the State Department considers "camel jockey" as one of the largest destinations for what they call "human trafficking" - along with "prostitution" and "forced domestic servitude" so it's supposed to be very big and very exploitative...