He still technically holds the title of president. You never lose the title, just the powers. Carter’s still President Carter. JFK is still President Kennedy. Trump is, extremely unfortunately, still President Trump. None of them get powers, but the title is forever.
Which, fair imo. It’s a position only 45 or 46 people out of millions of Americans have ever achieved (idk how they count the one dude who skipped a term). Keeping that title for life sounds fair to me.