As DM pointed out, the belt buckles in those pictures are not pointing directly at home plate. Furthermore, we can’t tell from the still photos how long it’s been since the front foot planted. We see that it’s planted but for how long? If the foot has been planted for any length of time, that means the hips have had some time to continue rotating beyond the point they were at right at foot plant.
As I said previously, opening the front leg and foot into foot plant usually starts to open the hips. So you will normally see the hips rotate partially at foot plant. But they don’t completely open by foot plant - they finish rotating after foot plant. It is possible for the hips to be completely open at foot plant but we don’t want that because that wastes energy.
Take a look at the clip of Mark Prior on this site. Mark is an exception in that he has the flexibility to open his front leg and foot into foot plant while keeping his hips completely closed. But ignore that. Just focus on what happens with his hips after foot plant. You will see that the front leg braces, the front hip stops moving forward, and then the back hip rotates around the front hip. Maximizing this whipping effect of the back hip rotating around the front hip maximizes the energy transferred from the hips to the shoulders by maximizing the stretch or ‘load’ in the torso.