I think you should already have a natural seam in the UV coordinates for all the polygons that make up each face in a solid. Like for instance when you have a cylinder, UV coordinates are not shared along the seam of the cylinder, only 3D points are shared there. I wouldn't think you should have to manually specify seams.

Anyway, it would definitely be more convenient to have this done automatically instead of needing to do an extra editing step.

That's kind of one of the additional nice things of using a NURBS modeler, since every NURBS surface has its own UV space you get a UV mapping for everything automatically.

- Michael