CNC "Outline" doesn't appear to work

According to The CNC outline option should look something like:

but when I try the same file with the outline option it appears to outline each individual line segment.

Looks like it needs to be a closed path for outline to work properly

It would be nice to get some detection for 2 points in the same location, but I can just edit all my files to make sure they are all closed polygons in the mean time.