Yet they do, even thicker stuff with bigger setups. Matter of fact, we don't even use skidsteers with mulching heads for clearing brush. Just a tractor with either a PTO mulching head or one of these brush mowers with chains that operates faster and at a third of the cost of a skidsteer while still producing very nice results. I'll go as far as saying that a 70 HP tractor will outwork a 95HP skidsteer.
In certain scenarios, the chains will actually work much better than blades or a mulching head. The biggest advantage is that chains don't care about rocks, stumps or whatever it's hidden in the brush.
I've done up to 3" easily with my little 35 HP tractor.
A couple pictures of my mower, which is a light duty one. The heavy duty and forestry versions are some bada$$ units made mostly out of Hardox steel and can/will eat some really nasty stuff.
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A couple of examples a brush mower with chains: