its so important to understand how the total movement range of the arm is build up.
Normally we only think of the shoulder as a ball in socket joint.
In fact its a ball in socket joint, but this joint in itself is also a ball in socket joint with a much greater absolute range of motion.
The bigger bal is the ribcage and the socket is the shouderblade with some supportive bones.
So first there is the shoulderblade that can rotate around the big ball, the ribcage.
This system carries the the miniature ball and socket, the humerus in the shoulderblade.
The rotation of the moon around the earth is like the rotation of the upperaqrm in the shoulderjoint.
The movement of the moon and eartth togetther around the sun is like the movement of the shouldercomplex around the ribcage.
Stretching the muscles limiting the range of movement of the small ball and socket usually is a bad idea.
There is just so much room before the upperarmbone or the humerus start hitting other structures or squeeze nerves or lubricating tussue.
Stretching the muscles that limit the sliding of the shoulderblade over the ribcage is a better idea.
Looking at it from this perspective its easier to understand why some stretches are bad and othere more save.