In regards to components of airspeed, we are not talking about simple vector addition here. Air is a compressible fluid, not a vector, and a pitot tube is not a magic measuring instrument, even for test pilots.
Anyone here fly glass gliders? Seen speeds of 5-20 kts on the airspeed indicator while in a sideslip. I don't think the wings were only seeing 5-20 kts of useful airflow.
Airplanes certainly don't stall when the airspeed indicator hits a certain IAS, they stall when the wing does.