In her article, which runs some 15 pages, Goldner touches some points mentioned here, early on summarizing major adaptations of the ballet since 1841, including just in passing the PNB one in 2011, saying of them, "None of these adaptations captures the spirit of Gautier," which she has elucidated with substantial quotations etc. by then, and in her discussion of other Giselles which follows she remarks that "...with all these ballerinas the smaller stuff is smudged. Carla Fracci fudges everything except when she dances with Albrecht. ... It's as if she's marking the choreography..."
This is in contrast to Verdy, who, realizing Gautier's spirit, dances full out just about all of the time but fully delineates the small transitional movements that give dancing its luster and energy. [Trying to paraphrase Goldner closely here.]
Maybe all this is takes us a little OT relative to Eileen's original question, but this article is such a good read, it has seized my attention!
Getting back, though, I'd like to point out that when Balanchine did stage Nutcracker, Swan Lake II (& IV), and Coppelia, he included major new choreography: Most of Nutcracker, except for "Candy Canes" and most of "Sugar Plum"; practically every other sequence in his S. L., or so it looked to me, comparing it to the "white" parts of the Royal's version at the time; and Act III of Coppelia, Alexandra Danilova having set Acts I and II according to her memory.
Part of an answer to why Balanchine did this and not that comes from his conception of what the spectators' experience would be. Remember his comparison of himself to a chef - he knew people who came in wouldn't enjoy eating beef three times - and running his company, where we fed our souls, he was not only making ballets, and assembling programs like interesting menus, but building a repertory serving us differently from others.