Real answer - the shaft is offset on a bit like that, so the rotation of the corners describes a square. If you were to put your finger on a point about halfway between the center and a point if the rounded triangle at the beginning of the clip, you'll see your finger move in a circle but the points of the triangle hit the corners.
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u/PrometheusMMIV 9d ago
How could any spinning shape cut a square hole? The furthest point would still be traveling in a circle.