If we play a random calendar on a stock with no event, we will profit from time decay like TOS expects on a day with the underlying unchanged. This is different.. Here, the model thinks several days of intense moves are expected in July, but really it is only one big jump.
So TOS thinks the July options should rapidly decay each day, but it really happens all at once after we react to the news.
It may help to think about what would happen if the report was postponed to after July expiration.
The July options would be worth very little and the calendar would be a huge win. And if it was put off to September you would be nearly wiped out on the straddle, with the calendar maybe a small win at best.