I've thought a lot about the height thing. It is easier to be thick when you are short. But, there are still ectomorphs who are short and and mesomorphs that are tall, just more of a rarity.
Definately shorter folks have an advantage in the mechanics of lifting. That's simple physics. While that doesn't mean a tall guy should make excuses, there are things that need to be considered. There are people who are built very different who would have very little stability when squatting. My gf for example, has very long thigh bones, shorter calves and an extremely short torso for her height. If you can imagine how that works, mechanically, it really gives her terrible stability problems when squatting. One size does not fit all when it comes to training. Though I believe everyone should do their best.
As far as whether Lee would be skinny if stretched, of course he would. But, that is never going to happen. I think what is being said is that given a certain amount of muscle fiber, it's going to look more thin when spaced out over a greater surface area. Compared to Lee I'm a skinny sonofabitch. I recently competed at about the same weight as him, but at 6'2". But, even shrunk down, I don't think my arms would measure 21". Lee definately has some great muscle mass, a great bodybuilder imo.
And, so many things go into the look of a person's physique: height, shoulder width, where the muscles attatch on the bone, muscle belly shape etc etc. Not to mention the person's genetic abilities to digest sugar, protein etc. and utilize it only as they can.
Jacob