Looked into this "sling shoting" phenomenon, motion(s).
Seems a complete waste of motion to me. A large movement that the open hand does not need to make. Just too many movements.
AND...there's a HUGE possibility of the "racking" hand slipping on the slide, for many reasons. Count the ways...rain, sweat, cold, mud, blood, (other bodily fluids!), squashed sandwich, loose jacket, being in tight space..!
There's no way that the "sling shot" motion is faster from...fresh magazine - to re-aim...than the two handed, drop the slide stop with the off-hand...by equally competent people performing their given practiced steps.
Or with the gun hand with a long enough or rearward positioned slide stop lever, than the gun hand thumb dropping the slide stop.
Mike
P.S. - And as far as part of the original post, one would have more to be concerned about if letting the slide run free will damage their weapon.