Why Didn't Truffaut Like It?

I've never seen "Poil de Carotte" since it is unfortunately not available in the U.S. these days (grr), so I can't comment on its merits, though I've heard only good about it. It certainly seems like it would be right up Truffaut's alley in terms of its subject matter. He was quite the opinionated firebrand in his early film criticism, and I wonder if he was merely tarring all of Duvivier's work with the same brush based on his opinion of some of the work he was producing in the 50's. I would have been willing to bet that with time, if he had lived longer, he would have been kinder in his estimation.
P.S. I have since seen this movie and, for the life of me, can see no reason for Truffaut to put it down. Its as empathetic to its misfit hero as "The 400 Blows" was to its' own. The mother is too theatrical, as others have noted, but otherwise the film is quite naturalistic, with exceptional for its time cinematography, a fine musical score and superb performances. Robert Lynen towered above other child actors of the time. Given their real-life fates, the ending scene with Lynen and Baur, already moving, is almost unbearable.