I wouldn't agree that's it's undeniable, I would agree that people are often confused by what they are seeing based on the myth of the "egg eater". Three generations of keeping chickens in this family spanning over a 100 years, all different breeds and large and small flocks, and we've never had a dedicated egg eater, so I'm naturally skeptical of what people are seeing there.
I think the stories are based on tales just like the one that started this thread and are taken as fact of an "egg eater". Egg eating typically happens most often twice a year...as chickens are coming into lay in the spring and going out of lay during the molt. If a person just waits that period ends and the evil "egg eater" fades into the flock, never to be seen again until the next time shells are fragile and easily damaged.
As this time frame usually last a week or two and even longer, by the time someone discovers eggs are being eaten, asks someone else what to do about it and then implements a "egg eating breaker" solution, the chicken's shells are already starting to firm up and the egg eating miraculously responds to the supposed solution. It's all coincidental~ and fanciful~ but not entirely factual.
Here's a little experiment to do the next time one fears they have an egg eater....don't supplement with calcium, proteins or any other nutrient, wait it out and watch what happens. No tricks, wooden eggs, mustard eggs or other such flotsam....just...wait. See if it doesn't go away all by itself and then you'll know it's seasonal, normal, and temporary.
I'm not saying it's impossible to have a rogue chicken that will prey on eggs but that's the exception, I've never seen it or heard of it in more experienced owner's flocks and if it were that common chickens would never have survived for thousands of years because they would have eaten any chance of their own offspring surviving and quickly went extinct.
