We could totally see someone leaving a complaint like this in order to get a free meal. A diner wrote a review that read: "The restaurant said children eat free but my 19-year-old daughter still got charged for her meal". Of course, there is a difference implied when a restaurant uses the word children and not sons or daughters. They mean that young children eat free and not fully grown adults who happen to be your children.
This is one of those things that we thought were pretty universally understood, but apparently not. We hope this was just someone trying to complain and get a free meal or something.