I suspect rather that the organization has let some thing slip that are uncomplimentary to Kate to lessen her power with the press when she marries William.
They seem to like Kate alright; she's low-key, discreet, and strong minded and she doesn't seem to play games with the press. However, the stories about Kate before the breakup were way too complimentary - she was portrayed as the perfect Princess in every way.
I think the Royal Family had understandable misgivings about bringing another 'Perfect Princess' into the family at least as far as her reputation with the media because if the marriage has any difficulties, the 'Perfect Princess' could turn around and use her media power against William.
A new Princess with a few minor flaws to her reputation is far safer for the Firm. If this is what's happening, then I must say its one of the rare cases where the RF is more saavy than the press because the press doesn't seem to mind picking up and running with uncomplimentary stories about Kate.