Yes, that is strange, in a lucky sort of way.
Do you have any other roosters that do crow within hearing distance? Usually cockerels don't need an example to start crowing, but I had one that did. A long time ago I rescued a cockerel from the middle of the highway that fell off a poultry transport truck when a door unlatched. His cage mates did not survive, but Frank became a pet. I did not know it at the time, but he was a "meat bird" raised in a small cage. He had to learn how to walk and drink from a bowl, but he was docile and very friendly... and he did not crow. Another point in his favor.
I warned the man who shared the small property where I lived... Do NOT CROW at Frank. I didn't even want that bird to know what crowing was. Well, months later this man had a friend over and he took the friend out to the barn to meet Frank, and guess what.... they crowed at my bird! And guess what... Frank immediately crowed back. A lot. And loudly.
I was not happy. I suppose Frank would have eventually crowed one day, but having an example certainly sped up the process.
On the flip side, I have also noticed that some young cockerels will not crow in a flock with an adult dominant rooster. Is it the influence of the dominant rooster, or are those silent cockerels just late bloomers? In a group of 5 cockerel Seramas I hatched, 3 of the 5 crowed a lot, one crowed seldom, and one never did crow... until I sold the other 4 and he was the only one left. Then he did begin to crow, but was never an over achiever in this respect.
Genetics? Probably.
Also, for you, winter is beginning and your days are short, and I think growth slows a bit during this time. Chickens hatched in early spring tend to mature and begin laying more quickly than those hatched later in the summer as the sunlight decreases. Sometimes pullets from later hatches will not lay until the following spring. My EEs are quite large and heavy birds, taking longer to mature. The hens' first eggs came at 29-30 weeks, but well worth the wait. So you may just have a batch of late bloomers. Very good looking late bloomers!
