I've found small changes in 'bar position can make it easier or harder to stand for climbing, in terms of the balance feeling right when I get up. I'd assume the pros have their positions a lot more finely tuned than we do.

Another thing is that it might be more efficient to climb with the torso up a little higher, and the hip closure angle (minimum thigh to torso angle) larger. Subtle differences in how and when the glutes and long back muscles are activated and brought into the leg thrusting?

It looks to me like the bottom line is that there might or might not be a benefit that you can find. You might want to experiment with small changes in handle bar height and rotation, and stem extension, and see if you can find a sweeter spot than you have now. I'm suggesting small changes so as to not stray too far from the position you have, which presumably works well. Record your current position so you can re-set the bike to it exactly if none of this dinking around proves to be of any benefit.

If you got an expensive fitting that uses power measurements and pedal motion analysis, you could probably get closer to the best optimization.