I know, I can change the order of languages in my browser so that "Moodle in English" comes in English. But there is a reason why I have the present order. (I have my priority of languages, that is the whole idea of the language setting!)
Note that, this happens if I am not logged in. I know the "Preferred language" setting in my profile. That is a new question, which should wait for a different discussion.
In fact, "Moodle in English" means a space where english is used.
It's not a course dedicated to learn English, so isn't forced to use english language for his interface. And lot of people prefer using there own language for the interface.
It's the behaviour I would expect if I was putting my browser into Welsh for example.
Thanks Séverin, I couldn't explain it better.
French is my mother language, but I happen to understand (more or less) some other languages. Occasionally I visit the community course in these languages, and it helps me a lot to have the GUI of Moodle not translated in the language of this community, to facilitate my navigation.