To many coats are falling into the sports coat category which really are not sports coats. Some tailors say that the hacking coat really is not a sports coat, and others say it is, in a round about way. Tweed and leather buttons make a sports coat minus slanted pockets. Smooth cloth is outside the sports coat relm. As is business suit pattern. Today many sports coats use a business coat pattern. The rules change.
Blazers have gone through a number of rule changes, too. The English have play cricket with white blazers that don't always include metal buttons. American barber shop quartets have colorful blazers. School blazers are unique, based upon school colors. If you read old tailoring books blazers were not finely made coats. Then in the 1940s customers started asking for them made up much finer. American blazers hasn't followed the rules of Britain. We on this side of the pond have made our own rules. And, they change too, as time goes by. Some years ago, one person who used to write here, had a summer outdoor afternoon dinner party blazer made of white and black striped cotton with black braiding along its edges, something that was common maybe a 100 years ago (probably further back). There are many examples in history of blazers that are not navy blue with metal brass buttons (brass doesn't rust, don't deteriorate in other ways, and good for salt water use. Which is why they are used for boating and ships clothing).
