There’s a reason we see the same upper body action in the elite of the elite across all upper body throwing motions (baseball, football, and tennis are included in the post above): It’s the most efficient.
If we ignore the lower half for a second, we can get a better feel for exactly what process the upper half is going through. Upon hand break, the throwing arm floats down. During this floating, we’ll often see slight pronation and internal rotation of the throwing side arm. This pronation/internal rotation then sets up the following action: external rotation and supination as the throwing arm gets flipped up and back into the line of the shoulders.
From there, the throwing side humerus/elbow work behind the torso, allowing the larger muscles to be stretched and utilized during the following acceleration phase. The hand works around the humerus/elbow, further delayed behind the torso.
The torso, following forward flexion + rotation, will then decelerate and the humerus/elbow will then be propelled forward.
The humerus/elbow will then decelerate, and the forearm/hand/ball will then be accelerated forward, from external to internal rotation, to finish the throw.
I dig into this process even deeper in my latest arm action post, which can be found here.