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).
In fact, the half ton even has a lower 6600 lbs GVWR, yet mechanically the trucks are the same. The F44 K1500 will have a lower payload due to the weight of the transfer case, front diff, etc, but it uses the same springs, brakes, frame, and rear axle as my light duty 3/4 ton 2wd.