I'm in the same boat (living in France, browser and google account configured to use English) and I've never noticed this.

Now I'm not a hardcore Youtube user, but whenever I browse it, French-titled videos are in French, and the same for English.

I'm mostly using Firefox on Linux, and occasionally Edge on Windows.

Do note that when rolling out features like these, they geoblock them, even on a per run basis, so it might be happening a lot throughout the world but it just hasn't reached your country. For an example, mobile YouTube in the US lets me minimize the video and multitask while still seeing a picture-in-picture window and the audio, while as soon as one lands on France that feature gets immediately disabled.

I've heard about different features in different regions, but GP is also in France.

I am also not connected to my account when I browse in Edge (it's my work PC, it also uses a separate IP), so I don't think it's related to the feature being rolled out on a per-account basis.

I'm in France, my devices are set to en-GB, I've watched only English videos (plus the odd French one) yet youtube decides to auto translate audio in German and lately in Spanish.

Go figure.