Interesting. It is filled on mine too. I guess it was just a part of a clean-up job when they put the paint on.

It's not a perfect job, so I can tell it's been done. I wasn't sure if it was that way originally or not.

Interesting you mention it being done that way on verts due to the body flexing. I was atributing mine showing a tiny crack near the window to the body flexing.