Isn't the "Oscillatory stall" as described the same thing as the "Falling Leaf" manoeuvre"?
It certainly sounds like it... this from Fighter Combat International's website (hope they don't mind me copying - I certainly spent enough money with them!). I did the Emergency Maneuver Training course with them and it's the same excercise as described at Turweston.
THE FALLING LEAF / RUDDER STALL EXERCISE
The Falling Leaf Exercise is not unique to FCI Emergency Maneuver Training. This exercise is a great opportunity for the client to observe and experience flight beyond the normal envelope at angles of attack greater than the critical angle of attack. In a addition to simply getting the students feet moving, the Falling Leaf Exercise is an excellent demonstration of the aerodynamic reality of negative roll damping, exponential drag affects and reverse aileron effect. The awareness of and first-hand experience with negative roll damping is important to the avoidance, understanding and recovery from the various stall conditions, specifically uncoordinated traffic pattern stalls covered later in the course.