I don’t know if this is a bug or just not a feature. Selected vertices shown in the vertex coordinate list do not update when you perform an operation on facets or vertices that move them. You have to close and then reopen the list to get the new coordinates or clear and reselect the vertices. I do this a lot when I’m building a simplified model from a more complicated CAD import. For me it’s just an inconvenient extra step in building a model. This usual involves selecting two vertices and pasting their coordinates into a spreadsheet that calculate things like lengths angles and etc… to help build, move or rotate a model into place.
Finally, for distance between two vertices, you can use the “move vertex” or “move facet” command and the base/target vertex options (it won’t calculate angle, though):