For a long time, there's been a feature where users who've contributed very little activity on the site, who later request deletion of their account, have their account deleted immediately upon requesting it rather than having to wait 24 hours before their account is deleted.
As I state in the above link, the previous criteria for users to be eligible for immediate deletion were that they've never posted or voted more than once. The criteria were, however, changed in August 2020 to having to have never posted on the site before and having less than 101* (actually 101 or less) reputation.
However, the help center page on deleting accounts still mentions the old, no longer correct criteria:
If you have never posted or voted more than once on your profile, it will be immediately deleted.
Can this page please be changed to reflect the current criteria? It should read like this:
If you have never made any posts and you have 101 or less reputation, it will be immediately deleted.
(To clarify, votes are no longer considered by the new criteria. Also, a community member did some testing and found that accounts with exactly 101 reputation are also immediately deleted if they've never posted.)