No, PE was full before the upgrade was won, so i'd guess that as my two upgrades went through from PE to UC, then two upgrades went from Economy to PE to fill my original seats.
Upper still had five empty seats during the flight itself.

PE on the 787 is relatively small (35 seats) compared to the other aircraft (46 A330Neo, 48 A330 and 56 A350) so you might stand more chance of getting a desk upgrade for those aircraft with the larger cabin.