Mine are smaller than many of my other birds of same age. But, leghorns & many of the other birds of the game type are typically leaner & slower to grow, IMO. I do have a roo and he hasn't been mean "yet" but we will see. I've heard some Andalusions were used -- not sure -- but they look to be a finer animal. For sure, they are not 1/2 the size of my BO hens, LOL.
The SBELs I have are definitely leghorn crosses. Now those two roos are aggressive. My two were monsters! Because of the cost, I hated to kill them so soon. Instead, I used water! They would sneak up and rush you, fling themselves at you. One day filling the waterers, I saw one doing his "dance" and then, airborn! I whipped around and sprayed him good!!! At the same time I gave him my loud, gruff, STOP IT command.
He shook off, sqwacked and left. Try two, another shower. I even began carrying a smaller water can with a sprinkler spout. Apparently he (they) are not like the showers because now, while they still attempt a flog once in a while, I would say it is 20% of before, in about 3 weeks. Now, if he confronts me, I give him the STOP IT command and you can see him thinking about it.
So the SBEL pullets were also of this finer build. When they began to lay, I noticed a growth surge, and they are still small types but, look more mature now. Hope my TBWs do the same. My first TBW eggs are on the "any day" wait now.