Why was an entire minor scene omitted from the French translation of "Harry Potter and the Chamber of Secrets"?

I'm re-reading the second Harry Potter book, this time in French, and I noticed an odd discrepancy. Here is the beginning of chapter 10, "The Rogue Bludger," in English:

Since the disastrous episode of the pixies, Professor Lockhart had not brought live creatures to class. Instead, he read passages from his books to them, and sometimes reenacted some of the more dramatic bits. He usually picked Harry to help him with these reconstructions; so far, Harry had been forced to play a simple Transylvanian villager whom Lockhart had cured of a Babbling Curse, a yeti with a head cold, and a vampire who had been unable to eat anything except lettuce since Lockhart had dealt with him.

Harry was hauled to the front of the class during their very next Defense Against the Dark Arts lesson, this time acting a werewolf. If he hadn’t had a very good reason for keeping Lockhart in a good mood, he would have refused to do it.

“Nice loud howl, Harry — exactly — and then, if you’ll believe it, I pounced — like this — slammed him to the floor — thus with one hand, I managed to hold him down — with my other, I put my wand to his throat — I then screwed up my remaining strength and performed the immensely complex Homorphus Charm - he let out a piteous moan — go on, Harry — higher than that — good — the fur vanished — the fangs shrank — and he turned back into a man. Simple, yet effective — and another village will remember me forever as the hero who delivered them from the monthly terror of werewolf attacks.”

The bell rang and Lockhart got to his feet. “Homework — compose a poem about my defeat of the Wagga Wagga Werewolf! Signed copies of Magical Me to the author of the best one!”

The class began to leave. Harry returned to the back of the room, where Ron and Hermione were waiting.

Now here is the beginning of the same chapter in French:

Depuis le désastreux épisode des lutins, le professeur Lockhart n'avait plus amené de créatures vivantes en classe. Il se contentait de lire des passages de ses livres à ses élèves en reconstituant les scènes qui le mettaient le mieux en valeur. Souvent, il demandait à Harry de jouer le rôle d'une créature féroce qu'il avait terrassée, délivrant ainsi tout un village d'une menace mortelle.

Ce jour-là, il fit jouer à Harry le rôle d'un loup-garou à qui il avait rendu forme humaine, mettant fin à la terreur que le monstre faisait régner sur les paysans du coin.

Lorsque la cloche sonna pour annoncer la fin du cours, Harry rejoignit Ron et Hermione au fond de la classe.

I'm sure you can tell it's much shorter. Here's an approximate translation of what it says. The first two sentences are more or less identical so I just kept the original English text.

Since the disastrous episode of the pixies, Professor Lockhart had not brought live creatures to class. Instead, he read passages from his books to them, and sometimes reenacted some of the more dramatic bits. Often, he made Harry play the role of a ferocious creature he had defeated, saving a village from a deadly menace.

On this particular day, Harry was made to play the role of a werewolf whom Lockhart had returned to human form, ending the monster's reign of terror over the local peasants.

When the bell rang for the end of period, Harry rejoined Ron and Hermione at the back of the classroom.

Notice Lockhart's entire dialogue is gone. The whole scene has been gutted. What happened here? It may not have been plot relevant, but little scenes like this, capturing the eccentricities of the characters, are exactly what make Harry Potter such a joy to read.

The French copy I have is from 1999, and although it doesn't specify its edition, I can only guess that perhaps the translator was working off an early draft of the book before its final publishing, and that perhaps JK Rowling added that scene later.

But I can't be certain. Why might this scene be missing from the French translation?