Mules are slightly smaller than their horse parent, and when they grow they share traits of both a donkey (the long ears), and the horse (color, tail, etc.). A Mule in the grass.
For example, a 2014 Ford F-150 is considered a half ton truck but most variants can carry a lot more than 1,000 pounds in the bed. Since these terms are probably not going away any time soon, it's best just to think of them as smaller, mediumest, and more than medium.. (Pause for laughter).
The popularity of trucks is bolstered by the fact that horsepower, hauling capacity, and creature comforts increase year after year. Modern half-tons not only do things that used to take a heavy-duty pickup, like towing more than 10,000 pounds, but they do so while giving back better fuel economy than ever before.