That's good advice.
What are you feeding them? Are they getting a well balanced, complete diet and enough protein? If you have multiple chickens doing it, I'd look at diet first, in case that contributed to egg eating becoming a habit. Creatures can develop cravings for foods that contain nutrients that are lacking in their diets.
Most chickens can eat an egg that is accidentally broken, without becoming egg eaters. Mine have only eaten a broken egg a couple of times over the years, when a pullet laid it in a high traffic area. Occasionally, chickens do become egg eaters. Once egg eating becomes a habit, it's pretty hard to break. As has been said, other chickens can pick up the habit, too, as part of flock behavior. If you are having a problem with multiple hens, I would definitely look at building roll away nests. At least you would only have to do that once and then you'd have the problem solved.