its for the same reasons. the first notch wont pinch unless you cut deep{no need for it} the plunge cut removes the center of the trunk leaving the hinge wood and the remainig outside . there is no way to pich your bar.
your way though allows a person to pick off chunks without tipping them over. kinda like a high tech snap cut. thats a nice saw todem pole. ps those stihls make good wheel chocks.
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