That same "digital grading" technique was used in the Lord of the Rings films at about the same time. (See the documentary about it on the Extended Edition of FOTR.) Partly it was done to smooth out material that had been shot in differing locations under differing lighting over a three-year period and make it look coherent when intercut, but it was also to push the eyepopping greenery of the Shire, the golden woods of Lothlorien, etc.
But that doesn't mean I think anything less of Roger Deakins. In fact, I think he's a genius: he's my favorite contemporary cinematographer!