He has no business working in the chicken department if he's giving out that kind of idiotic advice.
Unrestricted feed, except for Cornish X being raised for meat on mildly-restricted feed to prevent leg problems, yes. But his advice to mix scratch with the feed is the equivalent to telling you to feed your child on a diet that is half cookies.
The situation of game chickens in a tropical environment and dual-purpose/meat breeds in a temperate backyard is completely different. Your method should not be attempted anywhere that doesn't support a population of feral chickens already because that's an indication that the environment does not have the natural nutrients available to support a chicken that's not being fed by humans.
Your grandfather was probably raising his chickens on a diversified farm where they had access to the feed that the other animals spilled and were picking undigested grain from horse and/or cattle manure.
Additionally, chickens from generations ago weren't nearly so productive as our chickens today. In
this poultry book from 1921 they were recommending a feed and management system aimed at making chickens profitable by getting 100 eggs per year -- from LEGHORNS!
Today I get more than that from my Brahma, who is considered a relatively poor layer at about 4 eggs a week.
