The reason I say it was incorrect is because I have seen this dancer. She is a maybe bit more muscular than some other girls, but I did not see any fat on her. You don't get to be that muscular by eating "one too many sugerplums".
I see it as no different than a jockey being told he is "overweight." Is he "fat" in a general sense? Probably not. Is he "too big" for his career as a jockey, which requires him to be small and compact? Probably. Same for sumo wrestlers. Is a 6 foot 300 pound man "too small" in a general sense? No. Is he "too small" to be a successful sumo wrestler? Perhaps.
Here, whether any of us think it was the best way to state his opinion, the critic is most likely not taking the dancer to terms for being "overweight" or "fat" in a general sense. He was using wordplay (sugarplums) in the context of a Nutcracker performance to state that, in his opinion, the dancer's size/shape affected the performance of the ballet. He thinks her size was distracting (as was that of her male counterpart). This isn't a situation of "the critic hates fat people - what a toad!" He may, or he may not. From his opinion that the dancers' ize/shape affected the performance of the ballet we don't know one way or the other.