I remember during my CPL training we practiced for emergency descents, in the small cessna the drill involved, closing the throttle, RPM full fine, then roll into a steep bank and let the aircraft descend in a spiral.
Sounds like a potentially dangerous exercise for no realistic purpose apart maybe if the aircraft is on fire and you need to get down to land in a hurry. A fire weakened wing will soon collapse in a tight spiral and there is not much future in that...
Pitch into fine will possibly cause a prop overspeed at Vne in a dive and in any case make little difference to the rate of descent in a Cessna single assuming a variable pitch prop of course.
The steep bank is not only quite unnecesary but again potentially dangerous especially if you happen to enter cloud and on instruments. Unusual attitude comes to mind. Finally doing a tight high speed spiral especially in IMC or at night is a recipe for severe disorienation as well as over-stressing the aircraft.
Seems to me you were taught a gimmicky procedure by a flying instructor who should have known better unless he was trying to relive old times in an airline simulator!