This question already has an answer here:
In the past, if you undid the changes after editing a post, the event would not show up in the revision history.
Today, I noticed that a new entry is created, labelled "[Edit removed during grace period]".
A meta search for "[Edit removed during grace period]" did not show any results.
It's not listed in the List of recent feature changes to Stack Exchange either.
When was this bug/feature introduced?