Simms' breakdown goes along with what I saw, primarily a) the Saints defensive front four contained Dallas' run game and b) the Saints secondary remained in zone mostly. The passing attack barely attempted anything intermediate or deep and Simms quantified the reason well.
It would be a logical assumption the Cowboys practiced exclusively to recognize Saints' man coverage. Hopefully, that will not re-occur as the season progresses since it appears the offense must 'see' what the offense preps for or it is becomes stuck in neutral.
Now, there is little reason to think the coaching staff did not recognize the Saints squatting in an atypical defensive coverage for all four quarters. The offense has practiced for zone coverage in the past. The question becomes either "Were Garrett and Moore confident enough not to get out of the offense's prepped gameplan, expected the defense to keep the Saints' offense bottled up, and thought they could win a close game even though the offense's opportunities to score would be extremely limited due to the Saints' zone coverage"?
OR
"Were Garrett and Moore not confident enough to ditch the gameplan designed to beat man coverage and did not believe the offense would execute well IF the adjustments were made for zone coverage?"
If it were the former, it is a sure sign that linear thinking remains a Cowboys coaching trait. There should always be enough prep time devoted to preparing for what an opposing defense does NOT normally show in-game. If it is the latter, it does reflect coaching's lack of confidence in its personnel in executing what has not been primarily taught in practice in the week leading up to the game.
The latter is a troubling thought since it will give defensive coordinators a clear blueprint for neutering Dallas' offense. They can confidently switch to zone mainly if their defensive secondary strength is man coverage, knowing they can easily switch back to their base coverage scheme if Dallas' offense beats zone. They can prep heavy in pre-snap disguise if their secondary's strength is zone coverage. The next few games should give some indication how or if Garrett, Moore and the offense can adjust for this new defensive curveball.