So I don't unbalance the car when turning in. if you just down shift and brake you jerk the car and engine brake, if you heel toe you raise the rpm for the right gear and release the clutch so the car doesn't jerk and stays smooth.
Sadly, smooth driving doesn't make an understeering chariot like a Golf fast point to point...I find you need to trail brake to unbalance it, to get the rear to start to rotate in order to kill understeer. That's fastest for me.
Plus, the lighter the flywheel, the less the jerkiness when changing gear.
plus if you was to have a "dog box" you need to heel toe so you don't smash the gears.
If you have a non-synchromesh gearbox you may...if you have a dog' box you don't need to use the clutch once moving, just a lift of the throttle and a hard tug/push.
go on you tube and watch a rally driver heel toe. they have to because they are side ways into a corner and need to keep it balanced.
You see tham left foot braking for the same reasons.