How restaurant critics operate

I must admit that I don't know anything about how they do things in France, but here in the United States, I get the impression that most restaurant critics do not normally disclose their plans to visit a restaurant on a given date. Instead, they simply dine there on the same terms as any other customer, precisely because they don't want any sort of special treatment. In fact, some of the better-known critics have been known to wear disguises to keep from being recognized (e.g., see http://www.writerswrite.com/journal/oct00/richman.htm). Similarly, the Wikipedia article on the Michelin Guide also says that anonymity is very important to them. So presumably the critics depicted in this film weren't from Michelin. Are there other (non-Michelin) critics who operate in the manner depicted in this film?