I would demand they buy the car back if the recall effects its performance.
If they reflash these cars to a conforming strategy, it’s guaranteed to result in poorer performance and driveability on the road. It won’t affect the claimed fuel economy, since those numbers were obtained with the emission controls active, but it’s certain to reduce the real-world fuel economy, as compared to when the controls were not active.
I’m sure you’ll see class action lawyers on the television advertising 24 hours a day...