English embellishments

Whie hanging around on hold for an hour I took the opportunity to read some more of the French version of "Twenty Years After", going back afterwards to run a skim-comparison with the online English version I'd read. The differences really are quite considerable, but what gets me are the occasional sections where the translator has not just abridged the text when rendering it into English, but instead added in something that simply doesn't occur in the original.

— Ohé ! qu’est-ce que cela ?	"Oho! what’s that?"
— L’Éclair, dit le patron.	"The Lightning," answered the captain, "our felucca."
— Nous sommes donc arrivés ? demanda Athos en anglais. — Nous arrivons, dit le capitaine.	"So far, so good," laughed Athos.

I can see, after a fashion, the point of adding in the extra clarification as to what, exactly, the "Lightning" is, especially as for some reason the preceding allusion to the ship's name had been cut out, so it hasn't been mentioned for a while.
But changing Athos' quiet query into a jolly and out-of-character aphorism that isn't reflected anywhere in the original text (where a large chunk of the content immediately following that exchange is then omitted) just seems *odd*.

( Multiple French editions )