Unity colliders are not designed to be dynamically scaled or change in shape. That's just how its physics systems work. It's not specific to Spine.
Because of this, weighted bounding boxes and deform animations on bounding boxes will not work. There should be a warning on the component if you try to do this.
If the BoneFollower for the parent bone is set to follow the local scale, it will still try to apply it to the Unity Transform. And Unity's physics system's sideeffects will happen.