Hi Centaurus,
Depends on what is defined as stall. If stall means "a sudden reduction in lift" then both are "stalls". If stall is reduction of lift due to high angle of attack than only the "low speed" stall is a stall.
The mach buffet causes loss of lift due to the shock waves.
The (low speed) stall is loss of lift due to high angle of attack.
I guess that's why some refer to the mach buffet case as shock stall.
In our lessons the difference between mach buffet and shock stall was only that in the case of shock stall there is airflow separation, in mach buffeting not necessarily.
See difference between second and last picture.
File:Transonic flow patterns.svg - Wikipedia, the free encyclopedia
The effects on the aircraft are different. In our text book the shock stall effects are:
- possible roll (if it occurs assymetrically) -
- mach tuck effect