Seems like a very useful contribution to the discussion about what we mean when we say an interface is "intuitive." I wonder about the idea of "error recovery" in an "intuitive" interface design - especially as it relates to your comment that "Apple software is not more intuitive to someone who has been using nothing but Windows for the past 10 years."
A salient example for me is the way my iPad behaves. I'm probably not the only one to have had this experience, but I often find that I have moved my finger across the screen in a way that has changed a setting: I have changed the interface in some way - and I have no idea how I did it! Now I need "error recovery" - take me back to the situation I felt familiar with. But I have no idea how to do it. I often end up showing the device to one of my kids, who will say something like, "Oh, you just tap the screen there - it's easy." But it seems to me that they are operating in condition #1 - no gap between target knowledge point and current knowledge point - while I'm clearly in condition #2, except there is nothing in the interface design to help me bridge the gap.
I wonder if Moodle's designers have always been cognizant of the need to provide that bridge, bearing in mind that many, many occasional, non-expert users will spend time in Moodle. So in that sense, error recovery is more important than providing a slick, mysterious, Apple-like interface design that works only for people in condition #1. Maybe Moodle is still like early Google - making it easy for even cats and dogs to use (though of course Google has become more and more Apple-like, while retaining the surface simplicity).