I would have to see the fine details of the investigation. Not having seen it in detail, it's difficult for me to take a position today.
I know for a fact that French-speaking researchers and students choose to submit applications in English because they feel that they will be better evaluated by the councils and evaluation committees. Now, does this mean that these students are working in English or that this research is being conducted in English? I don't know.
The challenge of science in French isn't new. English is the language of science all over the world. If you go to Sweden, Germany, laboratories often conduct their work in English.