IsTrigger collider still causing RigidBody interactions?

I hope someone can help me out here. I have a sphere with a sphere collider and a rigidbody which are used to make the sphere roll away when given force.

I have also created and empty child of the sphere with a box collider that is set to trigger. For very specific reasons that'll take too long to get into, I need to use this second collider to probe the object with a raycast.

However, even with this box collider set to trigger, unity is now treating the sphere as a box, no longer letting it roll and allowing other objects to stack on top of it unnaturally. (see second sphere on top)

According to the docs: A trigger doesn't register a collision with an incoming Rigidbody. So why does this happen?

 

must have another collider somewhere on bottom sphere, or maybe it balances right on sphere top somehow, if place top sphere slightly left or right will know for sure.