This happens.
My MarkVIII doors both still open but I can feel the difference when it is jacked up.
My 77 Firebird, nope, no way. That thing flexed alot.
The question is why does your MarkVIII have more flex than mine....I have a sunroof which should not help.....Maybe look about for rust underneath or signs of a past accident.
If that all checks out, your door could just be closer being out of alignment than mine or just closer to one end of spec. Seems like the more of an art than a science fix.
If it bothers you and I suppose its possible you'll be more likely to "get locked out of your cars" when its on jack stands with the doors stuck shut, try jacking up your car with the door open and seeing what is happening when you attempt to close it, gently.