Changing Settings for Mesh Collider on Model does not update Prefab as expected?

I am adding mesh collider's to various models Via Import Settings, and re-importing the prefab it is attached to, to update the prefab with the right settings. However, the re-import and re-fresh do not seem to see the new mesh collider info on the Prefab. Instead, I am forced to re-make the prefab, which means I'd have to replace every prefab in my scene with the new one. Is there a way to do this more automatically? Is this a bug in Unity or is this supposed to be how it works?