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).
Re: how many tones can a tri axle log truck hold? I hauled poplar on a tandem permitted to 66,000 lb. and averaged 20 ton per load and stayed within the permitted weight. It was a dump box with log racks. Got $30/ton and hauled one or two loads a day.