CogSim
I don't understand how you reach the idea of a stall warning based on an invalid (or even a valid) airspeed reading, since stall warnings are (should be?) based upon AoA
Stall is due to too an AoA which
is outside the boundaries, but
stall warnings are in addition due to your AoA being
in danger of going outside the boundaries.
If your horizontal velocity is very low you have little lift (even if not stalled) and your downward component of velocity will increase so much that the AoA will go into the stall region.