I'm the person that mentioned Flock Raiser (20%) and I agree that excessive protein is unnecessary. .
Purina recommends either Start & Grow (18%) or Flock Raiser (20%) for free-range or confined flocks up to 18 weeks. In the article you linked above it says "Feed containing more than
30% of protein causes uric acid production which in turn creates an excretory load on kidneys." It also says "Excess dietary calcium... " and a few other things contribute to gout issues.
I'm surprised that you recommend giving Layer Feed to chicks of only 8-12 weeks old. Layer feed has too much calcium and can do damage internally. The youngest age I've ever heard was 16 weeks and more often 18 weeks. I much prefer to offer shell in a separate feeder to allow them to begin eating it voluntarily when their body requires it as they approach lay. Especially since many breeds don't lay until 6-8 months.
I do not feed layer ration to my chicks, I feed 17% crumbles.
That can be found at most Feed Stores, or, continue with chick starter.
But we never go into over 17% for growth, except for Turkeys, geese, Ducks & large birds such as Peafowl.
The excessive protein is too much, unnecessary, and a waste of money for raising growing-on chickens.
There has been a lot of this talk in the Buckeye threads & forums.
Some recommended flock raiser AND supplementing bone saw dust (from your butcher's band saw) and even more than that.
Time and again we were seeing Buckeye with gout.
Even on straight flockraiser, some had gout.
I do not take much advice from Purina, they are the ones feeding marigolds to your chickens to improve yolk color, which is in fact, just another food dye.
There are many more reasons why I disagree with them as well.
Most everyone agrees, Flock raiser, is for ducks, geese & turkeys, and we have always used it for Cornish meat birds as they grow so outstandingly fast.
But not chickens, and certainly not Bantam fowl.
I would rather feed chick starter until layer ration is needed.
You have to take in consideration, that our birds get alot more protein than just their feed.
That includes scraps & treats, bugs and vegetation.
That, plus the 20%, has been thought of as too much protein.
I agree.