You are talking about two different things. The pecking order is the social ranking within the flock between all chickens. Chicks in the brooder or with a broody start working on that as soon as they hatch and dry out, but in a mixed age flock, it keeps getting sorted until all chickens are mature. That’s not what you are looking at.
You are looking at flock dominance of a rooster. Some hens, especially pullets, may squat for anything in spurs, but many mature hens expect more of a rooster if they are going to have his children. They expect a good flock master to WOW! them with his magnificence and self-confidence, dance for them, find them food, keep peace in his flock, and provide protection. It takes a mature rooster to do that, not a young brat. Age is not the important factor, maturity is. I’ve seen a 5 month old rooster do that, but that is really rare. I’ve seen a rooster not do that until he was 11 months old. 7 to 8 months is a pretty good average but it can vary a lot depending on the specific rooster.