I'm sorry, but this is completely unsubstantiated bunk. You won't be able operate the slide stop but you will be able to operate the trigger?
Explain to me, exactly, what constitutes a fine motor skill and what constitutes a gross motor skill? Which muscles are in play when operating the slide stop that are not in play when slingshoting the slide? When hitting the slide stop with my left thumb, I merely press in and down from where my thumb naturally rests in my two-handed grip. To slingshot the slide, I have to change the angle of my left hand, grip the slide correctly, pull it back all the way and release -- if I release too soon, then it won't work. But that is somehow less complicated than pushing down on the slide stop?
People keep repeating this mantra over an over, never making any pretense of proving its truth, as if repetition alone will prove it.
I don't have to think about hitting the slide stop. I don't have to look for it. I don't have to feel for it. I'm no master class shooter, but it is automatic for me, and with a good slide stop in the correct position and a bit of practice, it can be automatic for you too.