My older brother is HG+. He is a "Big Executive" but when you take away his brief case and suit and tie, he is a social idiot. Fortunately he KNOWS this and rarely if ever speaks in social situations.
At work, he does speaking all over the world in several different languages! He can talk technical, science and Math, but nothing in purely social gatherings. I was always surprised he found a wife!
I think for everything there is a stereotype that evolves based on some observations, right or wrong and this just happens to be the stereotype of GT folks.
