The Cowboys were not the only team to not play their starters on offense during the preseason. I have heard several teams question their strategy after Sunday, including the Bengals who rested a lot of players because of injuries.
Personally, I would have played the starters at least a quarter in the last preseason game. But the Cowboys could not have envisioned that Tyron would get hurt after the last game and would need to shuffle the OL before the first game. I do question the decision not to play Tyler Smith at LT that last preseason game.
At the same time, I think Stephen is way off base by second guessing the decision. Hindsight is 20-20. If Tyron had gotten hurt in that last preseason game, Stephen would be questioning the decision to play him.