They probably say 'grow vegetables for a family of 4'. On 200m2, you'd have an abundance of vegetables, yes; at least in warm climates like in southern France. But not enough to be self-sufficient, and a 200m2 traditional vegetable garden is a lot of work, too (one day a week, averaged over the year, probably?).
Takes a bit more then that to make a 200m2 plot thrive. My experience has been that it would roughly equate to 3-4 days of 4-6hrs. That is assuming you are keeping on top of all of the tasks and not using any serious tooling. If you do that and have good conditions/knowledge, you'll see a density that is enough to provide for 4 and generate a small surplus.
