Not really. It's not about what is in one bite, it's about how many total grams of calcium they eat in a day, and even that is average over several days. One bite will not kill them.
If you read that article her chicks range with a broody hen. My broody hens raise chicks on grass, very little of what they eat is actually chicken feed. Most of the day is spent out on that grass pecking away. This is a totally different situation from chicks that are fed only chicken feed.
There have been a lot of studies done on excess calcium and its effects on growing chicks. The results are pretty clear. If they eat feed with the amount of calcium in Layer and nothing else, more chicks die than similar batches raised on lower calcium feeds. They cut chicks open to see the effects on the internal organs. They see deformities. These may not be enough to kill all the chicks and not all the chicks have these problems, but those with injured internal organs (kidneys and liver) are often not able to handle stress as well as others later in life and they may not be as efficient as they could be. Not all chicks die, not all chicks develop internal problems, but the evidence is really clear that some do if Layer is all they eat.
What does the guy or gal at the feed sore know about feeding chicks? If you chat with them a bit often not much. Some are knowledgeable, some remember their training, some know a lot more about building a fence than chickens. I've had chats with the lady that manages chick days at my local feed store, it's amazing how little she actually knows.
