From http://docs.safe.com/fme/html/FME_ReadersWriters/FME_Readers_Writers.htm#acad/ACAD_writer.htm, I find:

Prefer Writing Donuts as Hatches

This parameter can be used to change how donut geometries on features with autocad_entity attributes not set to autocad_hatch or autocad_mpolygon, are represented as AutoCAD entities.

If this parameter is set to Yes, and a donut is planar, then it will be written as a hatch entity. Donuts with three dimensions will only be written as hatches if they have a constant Z value, which can be stored as the hatch elevation.

If a donut is not oriented in the XY plane, then the feature must have autocad_extrusion_x, autocad_extrusion_y, and autocad_extrusion_z attributes set which indicate the normal vector direction, orthogonal to the plane of the object. If not, the hatch may have Z values dropped, to force it into the XY plane.

If this parameter is set to No, or a donut is not planar, then that donut will be handled like a multi-area geometry, and will be written as a block.

Note -- this is because the DWG format doesn't have a primitive type for polygons with holes. So we have the choice of either making a block, or going the Hatch route.

Hope this helps.

Sorry for posting in an old topic. But i have exactly the same problem. 'Prefer writing donuts as hatches' option yes gives me a lot of filled polygons/hatches. I like to have them transparent, in line with the drawing.

The option no gives me a lot of extra blocks. No option for me.

So is there any option to write the donut polygons in a normal way?