It's not oversimplifying, but you can't "group" an alloy based on hardness, if that were easy to do, Brinell would only have 4 numbers when it comes to soft metals. You could scrape with a pencil and say it is harder or not harder than the pencil, but it still does not tell you zip about the actual hardness. Just use the specific pencil that cuts it because that's the way the test and the standards were designed to work.