I’m note sure why you bring foreign-speakers doing their PhD in French (the one who does have outstanding language abilities btw), I’m speaking about research output in general. The few thesis I looked from my immediate research entourage are quite weak compared to the few I’ve read from my home country. There is definitely something different in the writing and the expectations between Europe and the New World. To be clear, I don’t think it’s a language issue per se, but a result of the difference in requirements to graduate. For research papers, quality went down because of the rat course.

I bring it up because having non-native speakers being a much larger percentage of the output means a huge hit to the average quality of writing.

I went to a top CS research school and there were several students from China that had such a high language barrier that their papers had to be professionally rewritten by a service the university offered. Their research was Amazing but motivating the problem, describing the methodology, etc all in English just devastated the signal.

So yeah, you’re going to see good quality French writing because French is no longer the lingua Franca of science so a relatively tiny minority of non-French researchers are going to use it.