There have been studies that show that excess calcium can harm non-laying chickens. The studies I've seen were on growing chicks and roosters. I have not seen any on broody hens or when they are molting so I do not know the effects on them. The studies mainly show damage to the kidneys but there can be liver or joint damage.
The excess amount studied was the amount in Layer feed. All they were fed was Layer feed equivalent. No treats, no foraging, so they could control how much calcium they ate. The damage comes from the total amount of calcium they eat in a day and that effect is cumulative. One bite will not harm them, it is the total grams of calcium they eat in a day. If they eat a lot of low calcium food along with the high calcium Layer equivalent then the likelihood of them being damaged drops. It does not go away but it drops.
To test the effects of excess calcium they observe how many on this diet die compared to others on a low calcium diet. The effects on growing chicks and roosters is that a few more die than on average. Not a lot, but a few more. But they also cut the birds open and look at the organs and body. Not all growing chicks or roosters show damage but enough do that it is recommended that growing chicks and roosters do not eat excess calcium.
I have a rooster and I almost always have growing chicks in my flock that forage for a lot of their food. I never feed Layer. I feed a low calcium feed with oyster shell on the side.