Yeah, as I understand it, Supreme Court Justices hire a lot of kids out of the most selective law schools in large part just because they can. Like, they may want interesting people from a variety of backgrounds, but they also want people who are very good at doing what appellate clerks do, which is a lot of legal reading, researching, discussing, and writing. And they can get all that with applicants from the most selective law schools.
So, often they do. Not as a rule, but very disproportionately.
Of course the vast, vast majority of graduates of even the smallest handful of the most selective law schools are not going to be Supreme Court clerks. So that specifically is not a particularly good grounds for choosing a law school.
But appellate clerkships generally? Yes, if that is a potential interest (for many it is not), you might want to have that as a factor in mind when choosing between law schools.