By both virtue of education and selection process, and given that their education was adequately rigorous, they've likely been working hard at academics for > 10 years, they had the mental faculties to understand everything in their field, and they're certified by grades from the most educated people in their field on the planet (same is true for other top universities, as well). There are far more problems with hiring 15 year olds at NASA than sheer volume of applications - I would advise you to think more deeply about what you're suggesting as, even in your alternative education scenario, it's a truly terrible idea.

Devil's advocate: why is that a bad thing? Kids get social/organization exposure, to sports, music, basic education. The motivated ones are still apparently rising to the top despite the shitty environment. Most humans don't need to go into rocket science, and half of your graduating class will end up directly selling things to other people (in some form or another).As well, are you arguing that kids need less social exposure? That would be true if most kids were going to become software developers, which is not the case. Most of our social interactions do not occur in childhood; you're not speaking for everyone.

What I will say, that is somewhat similar to what you're arguing, is that it would be great if students had direct access to more challenging curriculums at every stage of their education. To my knowledge, ambitious high schoolers need benefactors willing to pay for college courses that are standard fare for secondary school in a lot of countries. If you're naturally bright and hard working without affluent parents, you're SOL in HS, which is not fair, and I think it's also unreasonable that they need to rely on being autodidactic from a young age, which is really the only alternative.