It’s just an iteration over all Dualcells. As each of them is topological cube, Marching Cubes can directly be applied to them, even if there are a lot of edges of different lengths.
Here is the result:
As you can see, the flat areas got far less triangles. Here is again the triangulation of the same view with Marching Cubes, to show the drastic differences.
And with the accepted geometric error as parameter in the Octree generation, the amount of triangles is controlled.