That's just the following sentence in the book...

[AlainDellepiane]

The following passage is factually wrong. No "unnecessary word" was added in original the French translation.
What you're reading is just the next sentence in the book, joined with a comma (see below).
While I understand the utilitarian, educational goal of this example, it is disparaging to criticize a totally fine translation like this.
Maybe this could be edited and replaced with a made-up alternative translation, intentionally worded in order to be inaccurate?

"However little known the feelings or views of such a man may be on his first entering a neighbourhood, this truth is so well fixed in the minds of the surrounding families, that he is considered the rightful property of some one or other of their daughters."

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TextBlob does a pretty good job at the translation: "C'est une vérité universellement reconnue, qu'un homme célibataire en possession d'une bonne fortune doit avoir besoin d'une femme!".

It can be argued that TextBlob's translation is far more exact, in fact, than the 1932 French translation of the book by V. Leconte and Ch. Pressoir:

"C'est une vérité universelle qu'un célibataire pourvu d'une belle fortune doit avoir envie de se marier, et, si peu que l'on sache de son sentiment à cet egard, lorsqu'il arrive dans une nouvelle résidence, cette idée est si bien fixée dans l'esprit de ses voisins qu'ils le considèrent sur-le-champ comme la propriété légitime de l'une ou l'autre de leurs filles."

### In this case, the translation informed by ML does a better job than the human translator who is unnecessarily putting words in the original author's mouth for 'clarity'.

https://github.com/microsoft/ML-For-Beginners/blob/main/6-NLP/3-Translation-Sentiment/README.md#translation-and-sentiment-analysis-with-ml