Are the doors supposed to "flex" when they close?

[Gibson]

Hey guys,
Is the window frame of the door supposed to "flex" a little bit when the door is closed, or should the door be exactly the same profile as the body contours?

Here is why I ask:
I'm in the process of hanging new door shells (GM, according to the guy who bought them for me) with new hinges. I have the fenders off, and I have yet to install the glass and stuff into the door shells (wanted to do some test fits first). I took out the door gasket so that I could just have the door sort of "float" in the space without having anything resisting it. The issue I'm having is that even though the gap looks fine along the back edge of the door next to the B pillar, and the gap looks fine down where the bottom corner of the windshield and front door edge line up, the top of the door seems to be "inset" a bit. Almost like the door shell is not quite the same curvature as the body. I can push on it and get it to kind of flex and line up, but that just seems wrong.

Do I have something shimmed incorrectly? Shouldn't it match up exactly with the door opening?