ah, my bad...

when i said i made a nurbs shape i meant it was a primitive

but i think the edges still have to be attached in a certain way otherwise you don't get it extruded correctly when choosing polygons.

you can see in the image when i hit 3 then 3 edges appear smooth and the last one is hard edge because the verticies are not joined.

try it and you will see the issue i mean. + i will add a screen shot.https://www.minidavinci.co.uk/curve.jpg