John,
while simplification is often a Good Thing, the particular one of looking at high wing aircraft as pendulums IMHO is a bad one which has caused lots of confusion.
Looking at the force diagram, the lack of a moment arm between the lifting force and the resultant of the weight and acceleration reaction force is obvious - so where would such a righting moment stem from? And that's where we lost the readers with a grasp on physics.
I don't think the explanation of the
righting moment due to interference in high wing aircraft is too much to throw at people when discussing lateral stability.
Cheers,
Fred