Hi PaQ, I see - I'm not really familiar with some of these details on how Maya works, but it appears to me that the middle "subdiv surface" has already been divided down in those valence 5 areas.

So my guess is that a "subdiv surface" in Maya is some kind of hybrid object, which has already been prepared in its structure for converting to NURBS? Something like that anyway.

But if you continue that edge loop that I showed above to the end of the shape in the original polygon model before conversion to "subdiv surface", it will probably simplify that area that you were pointing at with the red arrow above.

You can't always avoid such areas, but in areas that you can it will probably make the result more simplified.

- Michael