The majority of backyard hens in the UK get fed a 16% protein feed.
The average egg contains 6 grams of protein.
That leaves 10 grams for the hen.
I haven't read anything about laying hens eating 16% protein feed falling over dead from malnutrition.
This would suggest that a laying hen manages on 10 grams of protein for her own needs.
The Ex Battery hens at the allotments were lucky to get 12 grams of protein in total until I arrived. They still laid eggs and grew feathers and, on average, lived as long as the average Ex Battery hen.
In general, moulting hens stop laying eggs. This means all the protein goes to the hen and none to the eggs.
Taking the 16% feed, this means instead of getting 10 grams of protein, she now gets all 16 grams.
Those who advocate higher proteinn diets for moulting hens, whether they are laying while moulting or not, often suggest 20% protein feed.
By the UK rough averages above that's twice the usual protein intake for a moulting hen that isn't laying.
If I doubled my protein intake I would not only end up wasting 50%, I would probably have other health issues as well if I wasn't involved in a high protein need sports activity for example.
Most people eat more protein than they need. This is particualry true in the USA and it seems possible that this overconsumption has been passed on to their chickens.
If one looks carefully at what we (humans) eat in a day, one has to work quite hard to maintain a diet of natural foodstuffs to maintain even a 20% daily protein intake.
The assumption that more is always better often doesn't work out to be the case with a little reasearch. Better quality however may work out to be benificial.