I've built the only machine that involves the supination of the biceps as well as the typical flexing. I have a patent for that invention. So I am not sure what Bob means by inner and outer heads. Larry Scott believed you could elongate the biceps by doing curls where you put tension on the biceps in the stretched position. Larry did have probably the best shaped arms in bodybuilding. Did his methods work? I can't say.
If you look at the arms of Arnold you find that one is peaked more than the other. Sergio had flatter arms no matter what he did.
It would be my guess that training for shape is probably not what happens in muscles. Either fibres hypertrophy or they don't.
I don't agree about the forearms making the upper arms look small. Great forearms like Sergio and Lee Priest make the complete arm.
Squats don't target the quads equally on everyone. There are better exercises for that. Ditto bench presses for chest. Most of us would have had better chests had we never benched. Bob is right about the injuries from bench pressing. However, I believe the reason is because of the amount of weight used. Anything over 400 pounds is bound to cause permanent damage, eventually.
About squats making your hips wider. I haven't seen that happen with the women bodybuilders. If this widening happens shouldn't all women bodybuilders have wider hips? I don't think that is what we see. Bob is right about most people doing the wrong exercises for bodybuilding. The trouble is what do you replace some of those exercises with?
I have taken exercise physiology courses for my masters degree but my focus was the philosophy of science. I don't claim to be an expert in exercise physiology.