I have a trig function driving displacement in an AttribVop so it's perfectly symmetrical but when I look at the curvature created from the measure SOP, it's not consistent. See attached. This seems to always be the case with the measure SOP so I'm not sure if I'm the weak link here or not.
I would try to use the “measure curvature” sop from the gamedev toolset, its quite good and comes with more settings. Might also be a problem with your object(flipped normals, non fused points), try to run poly-doctor, clean, fuse on your object before calculating the curvature.