We've discussed similar things before. Sarosh did a bunch of experimentation.
Torsional resistance 'should' help maintain good orientation and spin control on the projectile. If you had no delay between your wrist input and the projectile, that would be ideal. But in practice, all you can do is have a change in the torsional stiffness and damping. *see video from Sarosh/Acroballistics on torsion
https://youtu.be/vOuRwrfA7GQ?si=v85IeztL8KIMRYq3&t=134" So basically, for best results, you need to match the torsional stiffness of the sling with the speed you are throwing and the weight of the projectile. For too heavy a projectile with not enough torsional stiffness, the sling cords will cross and can foul the shot (not a clean release). I'm not sure if there is a downside to better torsional resistance other than it usually makes the whole sling a bit stiffer, so it makes light projectiles release less cleanly.
Back to your original statement about pre-twisting the sling...
I have experimented with pretwisting the sling to try and get a hook or a slice with golf balls with pretty good success. Essentially twisting can alter the orientation of the release cord upon release to alter the orientation of the spin axis of the projectile and hence the direction of the Magnus force and therefore how it curves. (in case you haven't seen it
https://youtu.be/ESrvvBFcrWM)