if 10 team members can speak english and 4 members french and english, how is it helpful for the company for that clique of 4 to converse only in french unless forced otherwise?
It can be, if it helps them to have discussions at a level of detail or clarity that would not be possible for them in English. Of course it's important that they don't make decisions in this vacuum and that where necessary translation is done for the others.
I've worked in many multilingual teams and I doubt that enforcing 100% a single language to the point that you forbid even brief clarifying "aside" discussions in another language would improve overall results.
