The list does not include people who were retrospectively honoured with an Academy Award and were dead at the time the Academy made the decision to make the retrospective award.
For example: in 1993, seventeen years after his death, Dalton Trumbo was retrospectively awarded the 1953 Oscar for Academy Award for Best Story for Roman Holiday.
However, Hunter was merely a front for Trumbo, because Trumbo was on the Hollywood blacklist at the time and it was not possible for his name to appear in either the film's credits or the Academy Award nomination (hence, it was not generally known that he was the real screenwriter).
Similarly, the Oscar for Best Screenplay (Adaptation) for The Bridge on the River Kwai was originally awarded to Pierre Boulle, but only in 1984 corrected to honor the actual screenwriters, Carl Foreman and Michael Wilson, who were blacklisted at the time and could only work on the film in secret.
By the time this correction was made, both Foreman and Wilson had died, but the award does not qualify for an entry in the above list.