Again, many thanks @bluemarble. I, too, can confirm that QV made only a cruise-by to St. Helena during her 2016 World Cruise, in April 27, as did of Ascension two days later. Incidentally, in this cruise she made her maiden call to St Vincent, Cape Verde (May 3), although she stayed there only for half a day. Nice itinerary, pity that she did not repeat it, as far as I know.
On the other hand, QM2 made a full stop in St. Helena in March 30 2010, time appear to be 09:00 to 16:00, on her voyage from Cape Town to Rio. Incidentally, as many here certainly remember, her 2010 World Cruise was her first one not circumnavigating the globe and the penultimate one that called to Rio. We were lucky to visit RIo on her World Cruise the year before.