@Data10 most elite private prep high schools don’t rank specifically not to disadvantage their applicants. That is likely why so many Ivie’s may not have that data for a lot of their enrollees. Although harvard says on it CDS it does not consider class rank for Princeton it checks the most important box for class rank.
Further in some states including mine, by law the official transcript reported to colleges must include class rank.
here’s princeton’s https://registrar.princeton.edu/university_enrollment_sta/common_cds_2017-2018.pdf
so I guess it depends how much a kid wants to trust AO and what they say on their CDS. But yes many explicitly check the box about considering class rank. (another area that benefits the wealthy that send their kids to private schools)