Normally, a high wing loaded aircraft will generate maximum instantaneous turn rate at corner velocity - that is the minimum speed at which maximum G can be obtained. Instantaneous turn rate is lift limited.
The creation of maximum lift causes a rise in induced drag and it is unlikely that corner velocity will coincide with maximum sustained turn rate unless the aircraft has lots of thrust to balance the drag increase.
Corner velocity is important if the ability to achieve max turn rate is required for defensive manoeuvres - fly below or above corner speed and the ability to achieve max instantaneous turn rate suffers.