WT to WT+ requires no change in catering at all, hence it's easy.

Who knows the exact mix of circumstances - maybe the CSD had an emergency of some kind to deal with and didn't have time to do upgrades on the ground. I imagine they'd (rightly) prioritize sorting out anything which endangers an on-time departure in advance of 'niceties' like this. Maybe you should have asked again on board once everything was settled?