Pretty sure he meant to say 4th instead of 5th... but then he's talking 10.5s which I have no clue about...
Wacker did a bunch of test and tune on this. The Auto shifts into 4th right before the traps. He made adjustments to keep it in 3rd all the way through and found it was better to just let it shift to 4th as it was dropping out of the power band in 3rd.