The real issue is math....a 30-team league with a 16-team playoff; mathematically, you'll always have at least one team with a losing record making the playoffs.
Not sure if that's true. If you have 14 really bad teams I would think the 16th seed could break even or be a game or two above .500
You're right, according to basketball-reference.com, its happened several times since the expansion to 30 teams.