I'm trying to render the geometry that is shown in the following screenshot (wireframe mode):

Click image for larger version. 

Name:	test_output_1175_zoomin.jpg 
Views:	326 
Size:	3.0 KB 
ID:	1081

This geometry is issued from dynamic tessellation, with fixed tessellation factors. As you can see, all vertices nicely join up, the geometry is "watertight".

Now let's see what this geometry looks like when rendered with a specific camera.

In filled triangles mode:

Name:  test_output_1175_filled_cropped.png
Views: 401
Size:  201 Bytes

In wireframe mode:

Name:  test_output_1175_wireframe_cropped.png
Views: 404
Size:  306 Bytes

Backface culling is disabled in both cases.

What a surprise! The GPU rasterizes more fragments/pixels in wireframe mode! It doesn't join up everything together when in filled triangle mode. In other words, filled geometry != wireframe fragments + some more fragments. How come?!
Is this expected? I don't see any bug on my side so far.
I'm on nVidia GTS 450 hardware and 320.18 drivers.