When a callback is placed through the In Queue Call Flow we see in testing that the callbacks are accounted for in audio PIQ messages in the call flow, but the queue dashboards do not show the call back as waiting. They do not appear as phone/voice interactions and aren't displayed on the main dashboards. You have to drill in to the specific queue and then they only appear in the "all" list, but still are not counted as waiting in the display.
To wit (naming redacted as a matter of privacy):
Main Activity Dashboard (note zeroes)
Queue Dashboard showing ALL interactions (note zero interactions waiting, but callback interaction in queue)
Queue dashboard showing voice interactions (note callback does not appear as a phone/voice type and is not tabulated into the number of interactions waiting on the dashboard).