The big bodied, tiny footed quarters were the result of halter shows and a new style. Only after those horses grew up, became lame at an early age, were bred and their foals did the same, was the style frowned upon. I had a big bodied, tiny footed quarter a number of years ago. I used him for light riding and trail, and he became navicular by the age of 5. This style was supposed to represent the quarter breed and did so very poorly by breaking down early.
It was my experience that people who owned these types of horses had sour horses because they were lame, and still ridden. A woman I once knew had a horse who was evenly navicular on both fronts so the horses didn't limp, he just stepped short. Since there was no head bob, she didn't see a problem, but he was in obvious pain and the " attitude" came out in bucking and being sour. Both his parents were champion halter horses with big bodies and tiny feet. Both his parents were chronically lame.
I haven't seen a poor attitude in a correctly bred quarter horse. My horse is an appendix and her attitude comes from her ADD and lack of proper training. It has improved immensely over the past 2 months though.