Bounds larger than expected

I'm not quite sure I understand how collider.bounds and renderer.bounds actually work. When I import a model from Blender (or create a standard one in Unity), the bounds look this way (just as I expect):

But when I rotate the model around global Y axis, the bounds transform and become significantly larger than the collider:

Why does this happen? As far as I know, the bounding box must always stay as small as possible, yet able to encompass the whole collider.

I'm using a very simple script to draw the box:

 private void OnDrawGizmos()
 {
       var bounds = collider.bounds;
        Gizmos.DrawWireCube(bounds.center, bounds.size);
 }

What confuses me even more is that renderer.bounds produce the same effect.