It works in that given example. Of course if you invent an arbitrary number it holds no value. But the OP postulates that through force of state having safety criteria restaurants must advertise is a systemic benefit to the food service industry, and if it actually
was, then restaurants everywhere would naturally adopt it if it increases consumer participation and revenues.
More than anything I'm trying to indicate that safety ratings are not actually benefiting the restaurants if they are not adopting similar systems elsewhere. And if they had a private rating system it would only mean anything if there was some consortium that posted standards. Consider the ESRB, which is not a state review board but exists to keep states from instituting review boards in the US on video games. They specify their rating criteria in available records and are utilized industry wide because the users of the rating board find it a net benefit.
I'm not going to argue that consumers do not benefit somewhat from food safety ratings, but it is also not purely black and white, because by compelling restaurants to produce them, if they are not a market positive effect (and like I said, the lack of a natural appearance of such a system outside mandate indicates it is most likely not) then the consumer pays for those reviews with a more significant expense on the part of restaurants than the restaurants make as a result of increased traffic, which means they must raise prices systemically to compensate, and you end up paying more.
Except in a sane market, you should be able to pay more if you want to only shop at restaurants that give safety ratings from some public consortium in the first place. But then you have the choice.