This doesn't stop companies from putting it in their contacts to scare you though. I worked at a FAANG in Berlin and that clause was _the_ reason I almost don't sign.
Unenforceable clauses are part and parcel of the typical employment contract in France. Non-compete are the one of the most common offenders. I have seen companies try to enforce hours while paying by the day - two incompatibles provision in French labour law. Most employers know they would lose if it came to the worst but they try anyway.