I believe and might be wrong buts its to do with high wing aircraft. And lack of good look out with the wing dipped all the way round. Where as square work for both high and low winged aircraft.
There is something wrong though with the instructor throwing it around at 500ft doing 60 deg banked turns in order to expedite the circuit ending with the student brain dead as you wang it round on finals while haulling all the flap in and suddenly ending up configured, on speed and on profile at 200ft.
Yes piece of piss to do when you know what your doing and current on the machine but it doesn't exactly create a good learning enviroment or for that matter teach good habits.