Yes. The gun wants to roll upward. With all four fingers on the grip it can roll and the fingers can slip, especially with smooth grips and/or wet hands. You wind up with the web of your hand up near the hammer.
With the pinky curled under it acts as a ‘stop’ the gun cannot slip because the pinky keeps it in place. When the gun tries to roll up, the bottom of the grip frame has to roll/pivot down and forward. It can’t do that with your pinky curled up under it. Rather than relying only on the force of friction of all 4 fingers on the smooth fronts strap, the pinky mechanically prevents the gun from slipping.
