sorgesu wrote:but there is space all around the doorway. Why is there no face in that space?
I thought the script fills in a face everywhere
The script attempts to work out what is solid and what is void, so it doesn't (usually) fill in every available gap. To see this draw a rectangle and offset it and pushpull it into a 'wall', reface the top and pushpull to make a quick floor and a roof; then draw a rectangle onto a wall face and pushpull it through the wall to make an opening. Now make a section cut across the wall passing through the window 'hole'. Use SectionCutFace on it and you'll get a filled-in section as you expect. But if you put a face or faces into the window as a 'pane' it can get confused as to which is solid and which is void in the cut. Usually if fills them all and you can then edit the section face group and select and delete unwanted faces, or redraw edges to (re)face something that's missed... Overlapping solids can confuse it as there's no simple rules to work out what's desired to be solid - typically the outer areas get filled, then any inner islands are emptied, then any nested islands filled etc (like CAD hatching ?)...
It's not foolproof...you should be able to make quick manual fixes to complex sections that get confused.