I don’t suggest that he did, but there as well could be different problem with this upgrade that we’re not aware of, which made them abandon it.
I just struggle with the notion that it’s conspiracy just to hamper Webber’s performance. IF they had option to run it or not and chose not to just to avoid giving advantage to Webber it would be as you say pathetic. But i will say again – giving it to Webber also helps Vettel in the long shot, they would gather data by testing it and prepare tweaked version for Vettel for Spain.
As for bringing upgrade for only one car – there’s ample example that the teams just may not have enough time to prepare upgrades for both cars before the race weekend, most teams did this in the past, and rear upgrade isn’t a small one.
One more thing – Webber was reasonably happy after the race, do You think he would be if he knew that the upgrade that could provide him with race win was laying around unused in the garage?
Don’t put bad will as an explanation when there could be other, simplier reasons.