Yes! You are right :-)

But for sam's case it works! ( I mean if he generates the back part using boolean subtracts and then selects just of face he would be able to extract outlines for his laser cutting project ) :-)



1- shows the object generated using boolean (subtract)
2- if you select the face shown and then using the script you are able to select edges connected to that face
3-Outline which is needed for Sam's laser cutting project :-)