For a very long time, posters on the misc had 48 hours to edit or delete posts. If someone wanted to change a post beyond that time frame, that were out of luck. Then around 2019 or so, the admins there decided to lift all restrictions of time limits to delete or edit posts, meaning users could then go back and delete potentially any post they had ever made, unless it was a post stuck in a locked thread. Pretty sure they did that because they were tired of people begging them to let them delete old posts over the years, so they enabled them to delete individually whenever, even if that was an extremely inefficient way of deleting posts.
Then there was the mass post deletion script that someone made to streamline mass post deletion rather than taking the time to individually delete them by hand, which took an eternity to try doing it that way. Then certain users like monsterpeed0ultra would run the mass deletion script once every month or two to wipe out anywhere from 500-ish to 2k-ish posts at a time