You can chalk that up to advancement in tire technology, as MTs don't need to be just blocky pieces of crap that can only do one job. Modern MTs can have almost all attributes of a good AT tire (granted, at the expense of certain things, like tire wear.) Softer compounds (great for grip, bad for life), siping in key places, solid lugs in key places, etc, makes modern hybrid tires the best of both worlds. If you look closely, you can see the STT pro looks VERY VERY similar to a duratrac, only with slightly larger lugs in certain places, and a bit less siping.