In animation, moving the arm without shoulder engagement can make it look disconnected or "broken," lacking natural flow. Adding shoulder movement supports the arm, creating a more believable, anatomical motion that reflects how bodies move in real life.
Finally was able to figure out how to somewhat simulate muscle tissue thanks to @JoeFixi82003985 without having to make weird shape key stuff, still early but it already looks a LOT better than before.
Its basically using the stretch to constraint where the muscles are. #b3d