I'm not sure either way. It really doesn't matter who starts because that is the person the coaches feel gives us the best chance to win. But look at like this:
Denard needs to get some confidence back after passing so poorly. So he was put with the better receivers and offensive line and the weaker d. He's got higher chance of success with that than what he would have with the second team o.
Tate on the other hand has proven to be a good qb and the best way to push, challenge and further develop him would be to give him the second team o vs 1st team d. Rich Rod say multiple times he was challenging Tate during spring and think this was the best way to do it.
That's just my take so take it for what is worth.