Extrude Arc in Z axis - cross section through surface no longer arc?

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1

Quite confused here. I have imported an arc via rhynamo and extrude it, when i compare the surface on plan with the original arc it appears to have lost it’s shape.

arc
arc.png1076×574 17 KB

t2 = Vector.ZAxis(); t3 = t2.Scale(50000); t5 = t4.Extrude(t3);

 

Valid curve. Arc start = (350856.6698,468969.9639,0.0000) end = (386458.0438,471078.7445,0.0000) center = (364428.4284,541419.0102,0.0000) radius = 73709.2731 angle = 28 degrees

 

NURBS Surface “U”: degree =1 CV count = 2 (0.0000 <= U <= 1.0000) “V”: degree =2 CV count = 3 (0.0000 <= V <= 1.0000)

2

I guess the surf is ok while it is still in dynamo and the conversion to a rhino nurbs surf has distorted it? Could i have exported as a rhino extrusion somehow?