Not to speak for the programmer, but I believe the 3D representation shown in the preview is an open array of polygons with no volume. It is simply not be possible to calculate a volume from that visualization data created when a toolpath is generated. And without a significant rewrite of Create that would make it more resource intensive, it’s never going to do what you’re asking for.
That being said, I think a reasonable compromise in the Modeling workspace would be a way to interrogate a closed vector and provide an area. Then you could just multiply that surface area by the depth you expect to cut and come up with a volume for a pocket. What do you think, Rob?