If it is indeed true that "the P320 fires only with trigger pull," then why has it been firing while completely contained inside holsters with no hands on the gun? If you're going to say that the holster itself is pulling the trigger, then why have these holsters decided they only want to pull P320 triggers exclusively? If the argument is that in each of these cases, some obstruction got inside the holster and pulled the trigger, then why hasn't the same thing been happening with any other striker handgun besides the P320? Why was the P320 designed in such a way that it can fire so easily by something barely touching the trigger? Why are these cases only happening with the P320 and not other striker fired pistols? Don't you think these are fair questions to ask in light of the evidence?
The screw thing was merely demonstrating that the trigger only has to move a tiny amount - less than 1mm to both deactivate the striker block safety and put the gun into a dangerous condition. Isn't that cause for concern, considering the pistol is designed for duty use, carried in a holster, where someone is going to be moving around, possibly running, etc? The slide twisting part of the demonstration is illustrating two things - one, sloppy fit which changes the amount of sear engagement as the slide moves up and down against FCU rails, and two, that it approximates what happens in the real world when you move around and the holster is applying varying pressure against the slide.