There is a small subset of undergraduate students that go to public universities who are hidden high achievers with a very strong interest in an area of study.

There is a small subset of undergraduate students that go to public universities who are hidden high achievers with a very strong interest in an area of study. In this sense, they evaluate a college the way a potential PhD student would look at graduate programs - they are more concerned about the department ranking and research activity. If this were the case, a student might very well prefer UW, Berkeley, or UMich over Harvard, especially in a field like CS. From this angle, it shouldn't be too surprising that this sort of student student would be as likely to come from UW as from Harvard. There's no real point in averaging in a huge student body drawn largely from a single state vs a small undergraduate student body with no in-state percentage requirements, because these students are unlike the other students at either institution. While it's harder to "get in" to harvard as an undergraduate, let's face it - the vast majority of students at either institution are probably not among the very brightest of the very brightest. Those statistical oddities are a small sliver, and I actually suspect that they can be difficult to detect through test scores and GPAs earned from age 15-17. These students often just don't give enough of a crap, or they may be far too focused on their intellectual interests to put enough time into the GPA game. If UW has a strong CS department, it makes just as much sense that these odd outliers would come from there as an ivy.