For tennis, hockey, golf and baseball etc. they get pretty good players. But, obviously these are players who put academics first and have the grades and test scores to prove it.
Of course, overall the very best nationally ranked athletes rarely go to Ivy or NESCAC in most sports. They generally aren’t academically qualified (like 95% of high school students in general), and generally spent most of the time on sports, not school.
Ivy and top nescac recruit a lot of the same players in many sport - I’ve been involved and seen it firsthand. That’s because the pool of academically eligible, realistically skilled athletes isn’t huge. When you look at national rankings, at least 95% aren’t going to be eligible at Williams or Amherst, or the ivies.
Your Harvard example seems reasdonable., although athletically Harvard gets very different athletes than say, Brown. The kid who went to Swat may not have been in the top 100 in California, but he probably was 200 or 300s. Which, in a state with thousands of high schools is nothing to sneeze at. In addition, he probably had a good and sat or act that met or exceeded the Swat average. Which, nationally is a fairly rare bird.