Spey fishing is quite new on Quebec’s rivers while it’s a very ancient technic as old as fly fishing itself.
Spey with two hands is very far from overhead cast. The learning curve is very stiff as you’ll have to reprogram your muscles and arms.
Why learn to spey cast with only one hand while the two hands spey rods are dedicated to this technic? Simply because buying a new two hand rod is expensive, this rod is cumbersome and it is far more easy to learn new moves than to reprogramm your two hand synchronisation.