Thanks to forum user Box for this tip!
Circle entities have a radius and connect multiple line segments.
These segments act as a single line in that they can define the edge of a face and divide a face. Additionally, selecting one segment selects the entire circle entity.
SketchUp’s inference engine still sees the segments in the circle. So, if you hover your mouse around the circumference of the circle entity, you’ll see endpoint and midpoint inferences.
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