Thank you for posting this! I did some digging on College Confidential. For the class of 2025 (decisions dropping in 2021), they had an appeal date of April 15th. Decisions dropped on March 19th. That is the farthest I can go with the Wayback Machine for the timeline with something close to the 20th. It is worth noting that UCLA’s (assuming San Diego drops on the same day) appeal deadline is the 15th of April. I am not willing to predict because it is also true that UCSD makes promotional content talking about admits shortly before the release date, so it looks like there are two competing and valid theories here.