The right key pin + driver pin is an usual pin stack.
But in each of 3 rows of pins there is one pin stack there, which has driver pin having a blunted cone on its top, and key pin which has a conic dimple in its bottom. Those are the left and the middle sets in the above picture.
What is the reason for such shape? I found only one - with it it's easier to find the plug resting position for key pulling out.