We replaced the hover over stat specific popups functionality with the stat details tooltip. At this point it is not possible to display the assigned stat specific popup instead of the stat details popup on mouse over. You can only see those popups via left clicking the stat in the HUD you assigned the popup to.
This feature request has been documented in detail and provided to the developers for future consideration. If you want to be notified if/when it is added please
send an email via the 'Contact Support' link and include "Notify Me When HMT-1361 Is Resolved" in the subject line and body of the email.