question about physical shape count

Filling the interior of a ship with solid armor blocks should reduce the interior geometry and thus the overall physical shape count, right? Yet somehow, filling in a massive section of my ship's interior seems to have no reduction of physical shapes. In fact, it even adds a few.

The info tab does indeed show that there are almost 100K fewer triangles (22,704,321 -> 22,604,177). But somehow it still manages to be more physical shapes after I fill in a large section of the interior (64,400 -> 64,404).

Does anyone understand how this is calculated, and why this is NOT reducing physical shape count even when there are 100K fewer triangles?

 

Please don't cross-post I answered you on your first post.