Hey, thanks for your response 
So if a door ‘trims’ a wall, I get valid references…
But if a wall ‘trims’ a wall is not valid…
I guess that’s just how it is…
As you note, it is a funny thing that 1 wall is randomly deemed the cutting wall and the other isn’t.
I guess that just reinforces that this method of getting references must be supplemented by a 2nd method for getting intersecting wall faces as shown here…
Edit: Insidentally, that method won’t return references of doors 
Only System Families… It’s all fun…!
Back to Python…!
Thanks,
Mark