If Jeremy Elliott's reporting is accurate, and there is no reason to think it is not, the series is the one who screwed this up badly. The white flag was thrown on what was scored as the final lap, lap 30. Sweet was third at this time. The checkered flag was thrown a lap later on the 31st lap that didn't actually count. By then Sweet had a flat right rear and had lost several positions. Only the podium finishers are to report to the scales.
Once the flagging error was made, any other way the series handled it would have gone over poorly. If an accommodation was made for Sweet, the conspiracy theorists would have gone wild. If anyone other than Sweet or Larson had been DQed in the same circumstances, many would be rightly enraged that the DQed driver got screwed by a scoring / flagging error.