I just sent a mass email to tons of LPs, whom I had filtered into their separate Stage groupings.  Hub actually did email everyone I selected (I could see that by checking my Outlook sent mail).  However, afterwards, Hub was misleading it what it showed me -- it deselected the first Stage grouping of LPs, but not the others (which incorrectly indicated that the others - who were still selected - had yet to be emailed).  Here's a screenshot of what it looked like AFTER sending to all of the following (7 LPs shown here), Matt Asano -> Mirza Ahmed: