I remember seeing somewhere that the Tufts dean of admissions said 78% of the applications this year were qualified students. We don’t see the exact stats, but the quote shows that college admissions are unpredictable. On a related note, a school might not perceive interest accurately. Last year I remember a fair number of students were rejected from Tulane despite 75th percentile+ stats and high interest, while others with the same stats were accepted despite using it as a safety.
Tufts accepts about 44% of the class ED, so its acceptance rate RD is especially low.