Yes to non-athletes.
Beyond that, as ski says, the criteria differ, and schools aren’t transparent what their criteria are, and I expect they might even change from year to year…so my personal experiences may not reflect the bigger/more complete picture.
Likely letter committees at the Ivies meet at least a few times a month throughout RD, and send letters out from the those meetings.
Early writes at Cornell COE and Vandy Mosaic are mostly URM AFAIK, happen in late Feb because there are campus visits (maybe virtual now) in March for these peeps.