I think an option on export would clue in the user that there is a difference. If I were a non-tech user, I would have given up and brute forced my changes into the table. Not only do the fields and columns have to agree but the content may need to be changed. e.g. an export of our lab reference ranges lookup table replaces a gender code with the person friendly "male" / "female". The import doesn't know what to do with "male" so it leaves it blank.