Thanks for the info... makes sense, but I'm getting a little bit different result. The 'Update All Segments' button doesn't seem to be working for me in this case. When I save the file and reload, it works.
For example, I just changed the material that is on the segment object. When I render the segment object, the material change is shown. But if I immediately render the RC object that uses the segment... the material change is not shown on the RC object (this is to be expected). But if I then use 'Update All Segments' button and re-render the RC object, the material change is still not shown. I try and use the 'UAS' button again and re-render... still the material change is not shown.
I then save the file and then re-load the file and re-render and now the material change IS shown on the RC object. So it seems the 'UAS' button is not working for me.