[graphviz-interest] Straight line drawn as a curve (Petersen.gv)

I'm trying to understand why Graphviz sometimes chooses to draw a straight line as a Bezier curve.

In the included sample graph Petersen.gv, there is a straight line from node 0 to note 5. But:

$ dot /opt/local/share/graphviz/graphs/undirected/Petersen.gv

produces output including:

	0 -- 5	 [color=red,
		pos="17,647.95 17,621.29 17,568.11 17,523 17,523 17,523 17,233 17,187.89 17,134.71 17,108.05",
		weight=5];

Why has Graphviz drawn this line as three connected Bezier curves? The X-coordinate of each point is identical; it seems that this could just as easily have been a straight line from 17,647.95 directly to 17,108.05.

$ dot -V
dot - graphviz version 2.32.0 (20130802.2235)


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