Thanks!

Kelly's motion is a bit hard to depict on a static equirectangular projection like this, so here's an animation of the motion in orthographic from 16 Ma - present (teal = Kelly, orange = Pruitt, purple = Sessions). You're completely right that there's greater spreading between Kelly and Sessions than Kelly and Pruitt; there's actually a bit of a rotational component to the motion between Kelly and Pruitt, which, combined with being relatively close to the pole, makes the motion a little weird looking in equirectangular. Hopefully that helps to clear up!

Click image for larger version. 

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