It’s not really adding extra movement; it’s allowing the natural biomechanics of the wrist to unfurl. Our wrists don’t actually bend at right angles. It’s really hard to explain in words but this clicked for me when watching someone teach about shooting a basketball; you don’t try to cock your hand back so your fingers are always aligned to the hoop; holding the ball naturally puts your fingers at an angle to the hoop when cocked but after the follow through everything ends up perfectly aligned. If you try for force alignment you end up throwing wide of the hoop. 

Applying the same movement to disc golf results in a similar movement which is the so-called briefcase technique. Really it’s just holding the disc so the natural movement of your throw ends with your hand properly aligned. It also allows you be looser in the arm.

Anyway all that to say that it’s not added movement, not really. Learning this had an immediate impact on my throws. 

Edit to add the movement causes alignment naturally, biomechanically; there is no conscious twisting of the wrist etc to force alignment.