Perhaps it is even simpler. The system interprets the difference between the current AoA and the stall AoA as a margin between the current speed and the stall speed. So in the example shown below, if the current speed is 120 kts at an AoA of 9 degrees, it would place the stall speed bug at 100 kts.
That suggestion seems the easiest for me to comprehend. Can anyone verify if it's correct? It seems elegantly simple.