I agree with @ucbalumnus that the admissions policies adopted by a need-blind school can be developed to help them achieve the desired mix of full-pay vs. those needing financial aid. Schools like Swat are up front that they are need-blind for domestic students, but they state that they “may be need aware” for international applicants.
The mix of first-gen applicants vs legacy, and the percentage of the class they will accept through ED, will undoubtedly affect this balance. Similarly, the percentage of students accepted from private vs. public schools can have an impact.
I take these schools with great endowments at their word - the admissions team does not know how much aid, if any, most applicants might need, Sure, perhaps they can get an idea if the applicant’s comes from a private HS and their EC involves rowing, and last name is WInklevoss (I don’t even know if they have kids ), or if they come from a public HS in a low SES neighborhood, and their biggest EC is working after school in a fast-food chain. I trust these schools when they say one of their goals is diversity, but I am skeptical that if both had identical test scores and stellar GPAs, both would have an equal shot - because I don’t know what else the school happens to be looking for that year. If they need a rower and they already have a diverse population in the incoming class, who knows?
@exlibris97 , when you cite hypothetical examples of a “highly rated” student being rejected because their “other factors weren’t that impressive” - can you clarify that by “highly rated” you are referring to test scores/GPA, and other factors refers to EC or something else? Does “unimpressive” refer to the EC’s being a dime-a-dozen, or does it refer to race/gender/geographic location, or is it their essay/teacher recs?
Amherst makes a point in their admissions info sessions to tell applicants that they routinely reject applicants with perfect SAT scores. Is this the idea you are getting at?