@
carleton,
Obree's hand position is an outlier compared to all others, so I will throw it out, because his hand orientation I feel is necessary due to the extreme nature of his position, mostly related to using his muscles to support his weight comfortably. In his position, steering feel and input is going to be a crude exercise relying on his lats for most of the input as the shoulders are going to be doing a lot of support work.
One reason the drop bar position work so well is that it allows one to lower their torso while keeping their elbows tucked in. Steering input leverage is consistently maintained across any range of vertical torso manipulation. One doesn't need to flare their elbows out and greatly cock their wrists to get down, like the guy jumping the rail. Drops also allow one to rock the bike side to side without flailing all over the place.
Having ridden motorcycles quite a bit growing up, that Duc has a fairly neutral clip-on position, and that's because it's a street racer. Track riders tend to bring their clip-ons in, closer to 45*, but their clip-ons also tend to be offset further forward as well. The more you move your hands forward compared to your shoulders, the more you bring the bars in. Conversely, the closer the bars get to a riders hips the flatter the bars get. Motorcyclists also tend to rely on countersteering versus lean-and-turn like most cyclists. A flared out bar helps with this. You can countersteer on a bike as well, but the forces are so low that very little input is needed. A motorcycle, because of the weight and speeds involved, needs more push on the inside bar to get the bike to heel over, and a flatter bar helps with this. The guys who countersteer the most have the flattest bars (flat track racers).
As far as Major's bar flare compared to the Duc? His bike's steering geometry (rake, trail, HTA) will be very close to the Duc, but very different from a modern bike, so there is that to consider.
As far as the barbell comparison, the clean and jerk is a gross motor movement, and the overhand grip is the most efficient way of pulling something up high from down low. Try the same movement using a Football Bar (which allows a neutral grips), it's nearly impossible, because you need to complete a curl once the bar gets to your hips. When doing a standing start, the handlebar always stays below the hips. A neutral grip (palms facing each other), doesn't compromise deadlift performance in getting the bar to the hips, so therefore, there is nothing negative about the position for standing starts.
So for drop bars: allows consistent steering input at all torso angles, allows maintenance of aerodynamics at all torso angles, allows one to rock the bike within their own space, doesn't compromise standing start performance, and provides more than enough steering input leverage to counter the forces needed to steer a bike.
Flat bars: Allow for larger steering inputs into the bar, allow for heavy countersteering, more ergonomic when bars are closer to the torso/hips in an upright position, but less effective at flatter torso angles.