You can live all your life in Quebec without even speaking one word of english.
We have laws to protect french, it's supposed to be the main spoken language in the workplaces, we have laws on advertising, we have laws on music on the radio, you can't put your children in a public english school if your not from canadian-english decent (so almost everybody including the immigrants)
It's also weird to me, but he's got the vocabulary, it's just that he has a very strong accent.
Most french canadians I know can speak english without any accent, but we always hear GSP in a public speaking environnement. I think he sounds better when he's on the phone or when he's in a one on one interview than when he's on a stage.
GSP also sounds off on stage when he speaks in french