With my chest and hips facing forward I can extend the right arm to the rear reaching back as far as possible and the left extending to the front as far as possible. This puts the right shoulder behind me and the left in front. So with my hips facing in a 12 o'clock position my shoulders turn to about a 1:30 position or 45 degrees. I suspect I am not anatomically unique in that respect. My upper chest does turn a bit but not as much as the shoulders.
Do you see JBC reaching his right arm to the rear. If not, your whole exercise is pointless.
The twist occurs because each rib is connected by a flexible joint to its own vertebra in the spine and the vertebra are connected to each other by flexible material that allow each vertebra to turn a different amount than its immediate neighbours. If a person has had back surgery resulting in fused vertebrae, the ability to twist is lost for those vertebrae. But Connally appears to have had a normal spine.
The wound was lateral to the lateral edge of the right scapula. It missed the scapula. The posterior border of the axilla or armpit is the lateral edge of the scapula. See:
https://teachmeanatomy.info/upper-limb/areas/axilla/
The author shows a diagram of the (left) axilla or armpit region from above which shows that the anterior surface of the scapula forms the posterior boundary of the axilla:

and from the front it shows the right axilla:

The armpit region actually changes depending on the positions of the shoulders and ribs. But you can easily see that any bullet that misses the scapula enters the armpit.
With Connally turned sharply right as he was in z254 in Altgens 6, the path from the SN looks like this:

Quit trying to play doctor. Your arguments are silly enough as a layman.
So by entering laterally missing the scapula it hits the fifth rib with a significant impact, deflects right, passes along the fifth rib to about mid-axilla and then passes through the fifth rib and exits an inch or so below the right nipple, (which has moved to the right).
I don't see the bullet path through JBC at z271 to be a problem if the bullet deflected to the right on impacting the fifth rib (and bending it so much that it fractured at the spine). I don't see how it could not have deflected given the evidence of impact. By deflecting, instead of going through the lung it went around the pulmonary cavity exiting below the right nipple before then hitting the right forearm.
All I can say is that the evidence says he was hit there (the first shot hitting JFK, the second hitting JBC which was closer to the third shot that hit JFK in the head). Not my interpretation of the evidence: just the evidence at face value. If you think it is impossible you need to show why. Just spewing a bunch of pejoratives at it doesn't do anything, other than lower the quality of the discussion.
In order to save this turkey of a scenario you dreamed up years ago, you keep sounding more and more foolish. In order to buy this crapola, we would have to believe:
1. Oswald fired at JFK while he was still passing under the tree when all he had to do is wait on more second to have a clear shot.
2. JFK and JBC were both hit at Z193, but neither reacted immediately. JFK slowly and calmly started to lower his right arm while JBC just continued to turn to look over his right shoulder oblivious to a deep puncture wound in his thigh.
3. Almost two seconds later at Z226, both men exhibited a delayed reaction to being shot at exactly the same instant when both men suddenly and dramatically flipped their arms upward, JFK in reaction to his throat wound and JBC to his thigh wound.
4. JBC began twisting to his right and doubled over in reaction to being shot in the thigh, even though he said he did that in reaction to having been shot in the back. Amazing how willing you are to disregard witnesses when they don't fit your BS story.
5. JBC, continued to turn dramatically in a clockwise direction until he was facing JFK and the shooter, all in reaction to being shot in the thigh.
6. With JBC turned to the rear and his shoulders roughly parallel to the sides of the car and Oswald behind him and slightly right, Oswald managed to fire a shot into his back near his right armpit, even though he had no view of JBC's back, and the bullet made about a 60 degree turn to the right to exit under JBC's right nipple.
7. After having fired his first shot, Oswald took 4.3 seconds to take aim for his second shot but completely missed JFK and hit JBC instead.
8. After missing JFK with his second shot after taking 4.3 seconds to aim, Oswald took only 2.3 seconds, the bare minimum time needed to fire an aimed shot with the Carcano, and made a precision headshot, killing JFK.
One of these items is hard to believe. It is preposterous to believe all 8 of these things could have happened. Do you ever wonder why after all these years, no one else has ever looked at the evidence and reached these same conclusions? Do you really think you have figured out something that eluded armies of researchers, both LNs and CTs, for six decades. You are a cult of one. That alone should tell you how silly your scenario is. That scenario exists only in your head.