> The employee has to tell the employer about any patentable idea, even if not in the general field of his employment, and even if having occurred after hours.

Just imagine the complete breakdown if a group of employees actually tried to go through with that: every wacky idea, from self-lacing shoes ("seem something similar in a movie") to bipedal gigawatt wind turbines that walk off to windier locations in a lull ("stomp, stomp, stomp! awesome!"). If they have to tell, some poor soul must be obliged to listen!