To add, allowing M+S means the whole thing is kind of a joke. As long as you don’t have a sports car with high performance tires you’re almost guaranteed to have M+S (or a variation) printed on the tire. There are no standards for including it other than “we think the tread pattern will work in snow”. The mountain snowflake symbol actually means something as there are standards such as the tires have to be made with a softer compound that doesn’t harden up like a hockey puck.