my 2c FWIW
use and amount of rudder depends on the aircraft.
eg from the flight manual of one aircraft I have instructed in:
"Alieron control response in a fully developed stalled condition is marginal. Large aileron deflection will aggravate a near stalled condition and their use is not recommended to maintain lateral control. The rudder is very effective and should be used for maintaining lateral control in a stalled condition with the ailerons in a neutral position"
That said, *full* deflection rudder in a stall recovery to stop yawing in a stall (as the OP is suggesting is being taught) sounds a little odd but is that actually what is being taught? And on what aircraft? Or is the instructor teaching the student to centralise ailerons and avoid controlling yaw with aileron by appropriate use of rudder?
2. Many students are scared of stalling. Which is sad IMO. When they end up as instructors that fear is contagious and the cycle continues. This is not a criticism of instructors but is something that good instructors should (and often do) work at correcting. Properly taught, deliberately stalling (and recovering) an aeroplane should not be something that instils fear in students for the remainder of their flying career. Sometimes it seems initial stall training consists of clumsy and rushed entry with the instructor's voice and demeanor on edge and with a pronouced nose high attitude and then a sudden drop that for a student who so far has only ever experienced smooth coordinated flight can be alarming.
Initial stall exposure should be gentle and give the student reassurance that they can handle the aircraft in all its normal operating envelope - it should allow the student plenty of time to experience how the aircraft feels at near stall speeds so their response and feel can become instinctive and they recognise the stall signs well before they happen and can recover appropriately and instinctively when they do enter the stall. (Which also is great for developing feel on landing).
Stall training should be fun not frightening.
IMHO.