I'm the opposite, never did direct arm work, just did curls and extensions at the end of my full body work outs. Started doing a day dedicated to arms and have put an inch on in a few months which is more than the last year so just shows really how people are different. But it could be because I've never intensively trained them and they're reacting to something new.
The more I look around I feel like Hoose is the exception more than the rule. Plus he is like 290lbs and moves more weight in a set than I do a week, he can feel anyway he wants about the subject matter. He has more than put in his dues.
But yeah, generally speaking people have to do curls, CGBP, pushdowns, skullcrushers ect... to get large arms.
By large I'm talking 18inchs or more. Although 17's would look huge on someone 5'8" or shorter. But again muscle shape and low bodyfat can make a 16 inch arm look huge and fantastic. I have no peak at all really. I'm going to have to push 18+ to really stand out in a crowd.
The whole "greek ideal" thing is neck=arms=calfs I believe. Well my neck is 18 without any direct training other than traps, so... I've got 1.5 inches to put on my arms.