As a french, I'm very surprised by this, as when I see a text in French side-by-side with its English translation, the English version is usually shorter. It may be a difference between speech and text, but it's still surprising.
I really thought the information density of French was pretty low, compared to English or Breton, for example.
I think that's due to English spelling vs French spelling. The latter uses a lot of letters to make a sound that could be recognized with simplified spelling. O = eaux
I think i read a study long ago, about the speed of transmiting information being faster in languagues of great empires. Sounds logical to me and matches English, French, Chinese.