Discovered that I was completly wrong!

Despite the fact that Amapi can work separately in Polygonal mode or Nurbs mode

The Old Amapi 7.52 can convert a polygonal model in Nurbs!!!
with 2 methods!
Without smooth
With Catmull-Clark subdivision

Reloaded here in Moi in 3dm format ;)
Works fine! :)
right bottom corner is the Amapi polygonal model