LoL I don't see anything serious to the proportions you implied. Nothing a simple band face pull and towel tuck cannot fix if they have tight chest and C1-7 issues.
Shoulder flexion and abduction are normal default positions for an average guy, wouldn't you agree? Significant? Not really, they all were in the safe zones, less than 45 degrees and elbows in front of shoulders. Maybe it's good for bigger biceps and lats? LoL Except for the innermost guy, who had his elbow way front and a bit hunched over, they seemed to have a natural spine. Nothing serious to complain about.
Plus people come in all different length and proportions, long short torso, humerus etc. As long as one can make necessary adjustments and have a proper sitting posture, with or without lumber support, I believe that would not seriously impede operations.
They are not sedentary office workers. They have morning drills, and most likely an onboard gym.
Regardless, I agree sitting posture is important.