This option lets you automatically convert editable poly objects that contain hidden edge turns to editable mesh objects whenever the plug-in detects them in the file.

Editable Poly objects in 3ds Max have hidden edges which can be flipped/turned to change their direction. Because FBX only stores edge visibility in exported files, not edge orientation, turned edges are lost, and the edges of editable polys export/import back to 3ds Max with the edges in their "unturned/unflipped" state. Activating this option means that every time hidden edges are detected, editable polys always export as editable meshes (triangulated in the process).

This option is active by default. Disable this setting to stop the automatic conversion.