The way it used to be taught on a basic level for little airplanes in the States was that you had a certain stall speed for maximum weight in straight-and-level flight. Let's say that was 50 KIAS. It would have been mentioned that this was due to airflow separation and that stalls could occur at any speed and attitude but here we are just discussing very basic instruction.
When you banked the aircraft then you saw the stall occur at a higher speed than that for straight and level. For instance at 60 degrees of bank that would have been 1.44 (the square root of the 2-G loading in a 60-degree banked turn) times 50, or 72. So, because the stall speed was high relative to the unaccelerated stall speed it was called a high-speed (more properly 'accelerated') stall.
The student was taught to recognise this sort of stall by entering a banked turn and then slowing to the buffet with recovery made by first levelling the wings. Since the aircraft was already above the unaccelerated stall speed that did the trick! It was a simple, safe way to demonstrate an accelerated stall.
Unfortunately, lots of students just remembered stalls as a speed-related, rather than an angle-of-attack-related phenomenon since that was the simplified way it was shown to them.
Shock stalls or high-speed buffet would not have been discussed at this level since light training aircraft don't get into that regime so that it cannot be demonstrated. I was interested to see it for the first time in a Cessna 441, since I had pretty much forgotten about it. The numbers were right, so where was this buffet coming from? Then I remembered that I was up at 25 000 feet, not down around 4 000 feet! Oh.