Bullet physics works only with primitives and meshes.
So, sphere has only radius to change, box has thee dimensions.
Your entity consists of two components - your physical primitive and your visible mesh. It you scale your visible mesh it doesn’t affect on your physical body. So you have to scale it too. But, as you can see, its not such easy.
Physics-based render can place your mesh on physic-body position, but scaling is not the same.
I can be wrong, so probably somebody more experienced will help you.
Also. I’ve done a nice script to use compound shapes, if you need it.