Bellard wouldn't apply and be interviewed like some Stanford grad. He would be head hunted and told he can do whatever he wants and receive a massive amount of compensation.
I'm not sure why you woulf assert he wouldn't pass the interview that seems totally outrageous.
Given his alma mater and the way the French education system works, he performed too-of-France at “solve math problems on a blackboard in front of someone” after two years of grinding math problems including extensive practice for the aforementioned “solve math problems on a blackboard in front of someone”. I think he could manage. FAANG interview is basically a CS khôlle.