Thanks for the clarification, Igor and Vlk. It’s pretty obvious when you run, say, Housecall that it’s rigidly following the directory structure, but there seems to be a fair bit of “jumping” with avast so it seemed like a reasonable assumption.
Admittedly with avast it’s often impossible to see the whole path that’s currently being scanned (at least at 800x600, and possibly depending on which skin), so I just guessed at what I’m seeing.