Normally stocks have been built to keep a individual standing upright, but now PD has determined that he wants Mei Mara to remain on her lips. More than this, he wants the position to be as uncomfortable as you can. Keeping her head shifted the way it is lets her see just enough of the room to know how much trouble she’s at. This vantage point is not any kind of advantage. It merely shows her that she has very good reasons to be very afraid.