Question How is rotation constraint calculated?

I need to update manually the rotation constraint component, calculate it (default component, not animation rigging one).

I have already updated/calculated the position constraint and the order of the sources doesn't matter. But apparently in the rotation constraint it does.
I've tried calculating it by "averaging" the rotation of each source in order, but I think I might be getting something wrong here...

Code (CSharp):

1. Quaternion quat = Quaternion.identity;
2. float weights = 0f;
3. for(int i = 0; i < constraint.sourceCount; i++) {
4.     weights += constraint.GetSource(i).weight;
5. }
6. for(int i = 0; i < constraint.sourceCount; i++) {
7.    quat *= Quaternion.Slerp(Quaternion.identity, constraint.GetSource(i).sourceTransform.rotation, constraint.GetSource(i).weight / weights);
8. }

With this code I expect to get the weighted average world rotation of the sources of the constraint, but it's not working...

 

My doubt comes from a test that I've made with 3 sources with the same weight and these rotations:

• A (0, 30, 0)
• B (0, -30, 0)
• C (0, 0, 0)

If I change the positions I get different results everytime in the Unity implementation, why is that? C shouldn't affect the rotation, but it does...