Ryan,
I assume you mean the Geometry Centerline that was introduced in WF5? The same type of thing was introduced for points and coordinate systems in sketcher.
If you create two identical sketches using a geometry CL in one and a regular centerline in the other you will see the difference. The regular CL will only be a sketcher entity while the Geometry CL will have tags and accessible in assembly and drawings. My guessis this gives a way to differentiate sketch CL's and CL's used on holes and cylindrical features relative to automatic layering (setdeflayer). In days of old, all sketched centerlines were thought of as axes and things that were not holes, revolves etc... that had centerlines had a way of ending up on a default "axes" layer. It was a pain to go in and remove those feature from the layer.
Hope it helps.
Dean
