It is true that all cockerels will eventually crow; some at quite an early age, some quite late.
I am trying to recall how it goes with a mixed pen of growers…
It is possible they crow less and later in their development. It’s also possible that six cockerels in a pen together will crow collectively less than they would individually if they were the only one in the yard. Part of this is that a bachelor group in particular form a sort of collective brotherhood that has different dynamics to one male with a group of females. The jostling and posturing for dominance and the friendship they have formed since young if raised together is a little unique.
I do feel that when I have half a dozen roosters on site it doesn’t seem like I have six times the crowing. Six roosters don’t “seem” to make much more collective noise than about two of them.
I think… (I might just become desensitised to the crowing after a point).
One thing I have noticed: if you have six roosters peacefully coexisting with each other and you remove one to take to a show or use in a breeding pen, when you return the extracted rooster to the pen with the others all hell breaks loose. They seem to have a very short memory.