That's the same information I've seen repeated over and over on sites and articles but they really have no studies or proof of this happening as there are no studies done on dual purpose breed chickens that free range and eat layer ration. Any studies done on calcium and kidneys were done on broiler birds in a controlled setting, which has no relation whatsoever to how much exercise a typical backyard flock gets compared to a broiler bird in confinement, not to mention that the genetics are completely different, with the broiler birds more predisposed to developing organ failure of all kinds.
Calcium is utilized in a chicken pretty much like it is in a human, the more exercise you get where the muscle exerts pull against the bones, the more calcium is removed from the blood stream and stored in the bones. In inactive humans...and chickens...the calcium is not needed in the bones as much due to low activity and no stress from muscles pulling against them, so the calcium from the diet stays in the bloodstream more and is then excreted by the kidneys...which is one reason young broiler birds are more prone to broken legs...it's not just due to their heavy and fast weight gain, but also due to inactivity and the resulting weak bone matrix.
In young, growing and active chicks, the calcium levels they require are much like a young child, puppy or kitten to form healthy bones and the same applies to roosters, which are the most active bird in the flock, with the largest bone mass. Whereas hens can utilize excess calcium in forming shells, they are typically less active than a rooster and have less large and dense bones, so it all evens out for them...the calcium is utilized in other ways.
As for practical experience with the calcium levels in the diet, we've been giving all ages and sexes layer ration for the past 39 yrs without a single bird becoming ill from any disease process in our flocks, nor any butchered bird showing any signs of renal disease in the organs. Typically we'll see what everyone else sees, friable, fatty livers in old layer hens, particularly those that have been exceptional layers...but all of that is common no matter what you feed.