Hi
most of the helicopters may have rotor stall during vertical descent with more than 500-700 ft/min and fwd speed less than 30 kts but this only matter when your blades are with positive angle of attack , so if you are in the same conditions but has your collective fully or almost down (0 or very little pitch ) this shouldn't happen ?
My consideration are in regards to approach to land technique with very dynamic 180 degree turns in forward flight like for ex. on below video (40 sec.) - this rotor didn't stall because the airflow was from below (desending) and it has some fwd speed .
https://www.youtube.com/watch?v=USmOqlj9Hag
Thanks for the fun video... As far as the commentary in the OP, the post can be edited, and you may want to open up any book on helo aerodynamics, and remove the confusion of your post. JD and crabby have been very polite..
Search for retreating blade stall, settling with power, vortex ring state, and open up a RHC AFM and read the notes on low rpm rotor stall.
Rotor stall is a very specific situation, and to be avoided. That a rotor stall event has occured is usually identifiable by the wreckage that the dead bodies are found in, and the unique bent blade shape.
Fly safe