I think there may be some confusion between crtitical AOA (CAOA) and stall speed. While the CAOA is fixed, the stall speed of the airplane is dependent on its gross weight.

When teaching full size flying, I introduce the critical AOA as the wing's max limit, and that in cruise, the pilot will generate whatever AOA is required to maintain altitude. The heavier the airplane, the higher the AOA to maintain level flight.

For example, let's look at two conditions in an airplane at 120 knot level cruise flight with an airfoil that has a max AOA of 15 degrees.

Case 1: For a gross weight of 3000 lb, assume the wing requires 5 deg AOA. We have a 10 degree "cushion" between cruise AOA and the 15 deg. CAOA.

Case 2: If we increase the gross weight to 5000 lb, the level flight AOA may be more like 7 degrees, leaving a "cushion" of 8 degrees before reaching the critical AOA.

If you reduce speed, you must increase AOA to maintain altitude. In case 1, we can increase AOA by 10 degrees before reaching the CAOA, allowing a lower "stall speed" than in case two, where we run out of AOA after only 8 degrees, resulting in a higher stall speed. [8D]

Similarly, if we bank an airplane in level flight, we use up some of the AOA "cushion" to maintain altitude in the turn... higher bank angle, more AOA required, less cushion, so the stall speed increases with bank angle also...

HTH

Jim