It’s like it changes the pivot point’s position according to the shape of the obj…
I believe that’s exactly what ZBrush does. It looks at the bounding box of your ZTool and puts the pivot smack dab in the middle of that box.
I think what most people do after they set up their blend shapes in ZBrush is export displacement maps for each one and animate between displacement maps in Maya. So you’re essentially blending between maps instead of point coordinate data.
I’ve never done it myself, but that’s my understanding of how it works. Someone feel free to correct me if I’m wrong.