I think you probably have a different idea about what constitutes success in higher education than the commenter to whom you're replying, and possibly also to admissions officers at prestigious universities.
It can be true that the SAT is a good predictor of university grades, and also that there is more to university life, and life in general, than grades. The parent comment is suggesting that optimizing for grades may not produce the ideal set of university students/graduates. But if you think that graduating with high grades is the whole point of the endeavour then obviously you'll disagree.
Certainly I enjoyed spending my time at university surrounded by people who had more going on than just academic excellence.
Of course there is more to university life than grades. But I strongly disagree with the comment that "all you get are people good at testing, and nothing else". I know a bunch of very high SAT scorers, many of them my kid's friends, and they are not just "good at testing". In general, they bring excellence and hard work to everything they do, including athletics, music and art. In fact, I'd argue that it's almost impossible to be "good at testing, and nothing else".
It can be true that the SAT is a good predictor of university grades, and also that there is more to university life, and life in general, than grades. The parent comment is suggesting that optimizing for grades may not produce the ideal set of university students/graduates. But if you think that graduating with high grades is the whole point of the endeavour then obviously you'll disagree.
Certainly I enjoyed spending my time at university surrounded by people who had more going on than just academic excellence.