From WT to WT+ any POUG should actually then rebook into and show P class, which is for WTP awards and upgrades from economy to WTP, to prevent the ticket being eligible for upgrading using Avios into CW but such a paid upgrade would of course earn for WTP.
However, that's assuming the initial fare was a revenue fare and not a redemption for which the latter would earn officially nothing. I can't see from the OP's post if it is a revenue fare or a redemption but maybe they will clarify? @
hmv