Sorry what?
In both pictures please remember that you're looking at sweep-oar rowing, so not both elbows will be doing the same. (Your outside elbow will be coming back further than your inside elbow)
Therefore in the first photo you should only be comparing S, 6, 4, and 2's elbows - their outside elbows. These are very consistent, in fact look practically identical.
The position of your elbow is not about "looking good". In fact very little in rowing is about looking good - except that usually if you look good (i.e. sitting up tall, straight back, good angles, good posture) then you can probably move the boat pretty well.
If you drop your outside elbow at the finish so that it's pointing down towards the water it will result in your wrists bending and you'll probably be feathering with your outside hand. Also it'll mean your outside shoulder will drop, causing your posture to loosen and you'll lose power around the finish. You should have a lean back, but with a straight back, and have relatively flat wrists so that you can tap down with your outside hand and feather with your inside hand.
Therefore boat speed will increase through the proper positioning of elbows around the finish.
Unfortunately (or fortunately maybe) boat speed will increase through the proper positioning of every single part of your body. Feet, legs, knees, bum, hips, core, chest, arms, neck, head. Yup, everything has a proper place and will increase stability in the boat