Try opening the doors in a unibody car with it on jack stands.
The engine, radiator, battery and suspension weigh a lot. The front frame rails are designed to resist compression, not extension. When the car is bare, that is 900 or more pounds NOT pulling down on the cantilevered frame rails.
My 70 Charger has no rust anywhere and has never been wrecked but the body gaps did change with it on a 2 post lift. Not a dramatic change but it was enough to cause the doors to drag a bit when opening and closing.
Opening and closing a 2 door coupe will have noticeable differences in the way the doors close on the striker pins when using axle stands on the frame. The stands aren't that far from the wheels on each end of the car but opening and closing a door, you can see how far out from perfect alignment the car is due to stretching metal when it's hung.
