Hello,
It's not just a display issue (I also wondered this), there is a gap, when I join all the surfaces together on this one it just comes out as one 'joined surface' rather than the 'solid' of the previous one.
Also if i try to use the 'Merge' function on the edges a couple of them just wont merge together.... I was going to 'Merge' then trim slightly differently.
Anyway i'm going to install the demo on my work machine tomorrow so if I can recreate the problem ill post a 3dm file.

Thanks.