No problem absent, actually Geneva is right on the French border, ans as you say, same language (but definitely NOT same accent btw).
Not germaine at all - as if you've not experienced this yourself, and seen it happen to many around you - it of course won't register. Most expats in France are there with spouses or family - so speak English part of the time, at least at home. If like me you have NO CONTACT WHATSOEVER with your own language because you are on your own, working and living 24/7 in a new language- then your accent does change. Really- and I am not the only one to whom it has happened. And to whom it is now happening in reverse- clearly. My English has really changed in the last few years since I am back here- many of my friends in the UK have said I was 'reverting'.
So if this guy is in France on his own, and lives and works with French people, possibly has a French GF- then he may well NOT be taking the *iss. It is actually very difficult to forge. Why take offence at my comments, which hail from long-term personal experience- not just with me, but others in the same situation. I know a few here on are in that situation right now- and we've discussed this recently.