Surely whatever it is that DP is adding in distributing the ball (not much!) is more than negated by him being worse than (in-shape) Collin at their job, defending.
One reason that I have heard is that with the new formation, Marsch needs CBs that can handle the ball well. The fullbacks are now up the field acting as wingers, so they can't do it. Collin is not as good dealing with the ball. Not a fan of the formation and Collin being benched is another reason to scuttle it.
Collin will get his starting spot back soon enough. He was atrocious vs Vancouver but DP is just not good enough to be starting over him in the long run.