The only way to create a rolling moment with the rudder is to induce a sideslip. Rhetorical question: Would we rather stall in coordinated or uncoordinated flight?
The scenario: Reduce the airspeed, add back pressure, ailerons neutral, apply rudder pressure. I just described entry into a spin. To me it sounds a bit peculiar to have this scenario described as the proper way to
prevent a spin.
What I was taught, and use, is to apply slight, smooth aileron inputs to keep wings level, using rudder for coordination. At the stall, ailerons neutral and use rudder to counter any yawing tendencies. If a wing drops at the stall, e.g. if one uses too much aileron or flies a plane that does have a tendency to stall over a wing, then that is just the way it is; it will be a stall with a wing drop. Recovery from a stall with a wing drop is something we all learned during training, right...?
Even if one uses too much aileron and provokes a wing drop, a spin should not result provided one uses rudder to counter adverse yaw and maintain yaw control.
Apart from my training, both standard references I use for basic flight procedures and techniques (the FAA's Airplane Flying Handbook and John S. Denker's See How It Flies) suggest coordinated use of aileron and rudder to maintain wings level during the approach to stall.
Nevertheless, intrigued by what I have been reading here in the last few years, I decided to go up and try the "keep wings level using rudder with ailerons neutral" approach to see for myself. I used a C172. After some rather spectacular departures for a C172
I decided it was just as bad an idea as I thought before I tried it.
The problem with that method, IMV, is what happens if it fails. If you manage to keep the wings level with small inputs, i.e., do not have to try and catch a wing that shows a tendency to drop with either rudder or aileron, both methods work. But if you fail, the coordinated aileron method results in a rather benign wing drop, whereas the rudder only method results in an incipient spin.