Get a nervous, heavy handed student to stall a C150 and see if you get an abrupt pitch change. CASA definition of aerobatics includes abrupt pitch change.
It sounds like his instructor had taught his student to haul the C150 into a steep nose high attitude for stall practice rather than lead into the stall in level flight at a reduction of one knot per second deceleration. That is how the certification test pilot does it. It is all about correct training.
Even if a wing drops rapidly at the point of stall it can be recovered quite easily if the correct technique is used. A wing drop at the point of stall is often caused by incorrect rigging and the maintenance release should be annotated "Aircraft un-airworthy" which automatically grounds the aircraft until inspected by an LAME and the defect rectified.
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