Again, I think (don't know for sure) Bennett was getting snaps leading up to the QB change. Just not at the beginning of the season.
The other side of the argument is that the game needs to played. As long as Bartel and Wallis were playing, they need the snaps, not some hypothetical might-play-if-I-need-him. A QB has to have some confidence and announcing Phillips as a potential late-season project and letting him take over the scout team or take 10% of the snaps with the offense would wreck what little confidence Bartel and Wallis had left.
Even in hindsight, I am not sure what Bennett could have done differently given the cards he was dealt.