I have heard of this trend in these sites of covering up when out and about with many people complaining - and rightly so! Clothes are an emotionally damaging force - they encourage not just the awkwardness of our bodies but trends/fitting in/judgement/dressing to impress etc are all things we wish to escape in a naturist setting and discourage the more easily swayed members of our families to get pulled in to. Before you know it those that wish to be naked may feel self conscious about being naked when others aren't and the sheep mentality removes the ability to make honest choices or even the fear of being teased. If these places are not careful they may find that they lose what makes them special. Naturist campsites are in my experience and research more expensive than non-naturist campsites (on the same level of features). We pay extra for the ability to be naked and to feel that being naked is totally acceptable and part of the ethos of those around you. I would not wish to pay to go to a naturist resort and find a lot of people dressed and start questioning when and where I can be naked. The whole point is to discard the clothes and not consider wearing them again and enjoy the holiday naked. 

France has some amzing beaches and venues, but it is a little less comfortable with nudity than we may assume. They do not have the primary idea that strictly speaking you can be naked anywhere in the countryside, beaches, rivers and lakes that the law in England supports. France has specified areas where you can be naked. You may feel that you can strip off on a quiet beach away from anyone but the law can decide to punish you for no good reason other than chosing to be innocently naked.