So you absolutely accept the word of a person with no expertise other than personal experience. Cath Andrew's is far from the absolute on raising chickens. Like the internet, not everything in books is what it may seem.And there is this: (just saying)
https://www.raising-happy-chickens.com/pasty-butt.html#:~:text=Chicks looked after by a,place of the mother hen.
My comments have been from personal experience. I have been raising chickens as long or longer than Cath Andrew's, so there is that.
I have hatched, raised and bred chickens for years. I offer my experience in the hopes someone may benefit, just as I hope to learn from others, so the wheel is not being constantly reinvented. If you don't like or agree with the information, feel free to ignore it. Just saying...