I don't think the (high rate) of legacy acceptances has ever been considered a secret at the top ivies? "Harvard's incoming class of 2021 is made up of over 29 percent legacy students, reports The Harvard Crimson." https://www.cnbc.com/2017/09/06/harvards-incoming-class-is-o...

At the school I went to, even before I applied I knew that their admissions process funneled legacy applications into an entirely separate pool from normal applications.