Please do not mis-represent what I have written. You state something as fact (“others…unambiguously treat graduate and professional school legacies identically…”) and then claim that is “contrary” to my “assertion”. I never said that there are no colleges that don’t treat them the same, just that undergraduate > graduate, which was based on the findings of a Harvard study (http://chronicle.com/article/Legacys-Advantage-May-Be/125812/), which found that…undergraduate > graduate.
Since you are being precise, what is your evidence for your “assertions”?
Oh, and OP: legacies are going down. In 1980, 24% of Yale’s incoming class were legacy; in 2014 it was 13%. Overall, about 10-15% of incoming Ivy students are legacy. (Source: http://www.nytimes.com/2011/11/06/education/edlife/being-a-legacy-has-its-burden.html?_r=0)